document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=115292>Question 115292</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Please help.\r<BR>\n" );
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document.write( "Solve the system by substitution.\r<BR>\n" );
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document.write( "3x - y = -7<BR>\n" );
document.write( "x + y = -9\r<BR>\n" );
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document.write( "Thanks<BR>\n" );
document.write( "JMS </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #83888 by </B><A HREF=/tutors/aboutme.mpl?userid=solver91311><B>solver91311(24713)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=solver91311><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=solver91311><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=83888\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Solution by substitution means that you need to solve one of the equations in terms of one of the variables and then use the expression for that variable in place of the variable in the second equation -- in other words, substitute it.\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3x-y=-7 ALIGN=MIDDLE  ALT=\"3x-y=-7\"   DISABLED_style= \"max-width:90%; height:auto;\" >.  Solve it for y<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-y=-3x-7 ALIGN=MIDDLE  ALT=\"-y=-3x-7\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=y=3x%2B7 ALIGN=MIDDLE  ALT=\"y=3x%2B7\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "Get the second equation<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x%2By=-9 ALIGN=MIDDLE  ALT=\"x%2By=-9\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "And substitute the value we found for y above (<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=y=3x%2B7 ALIGN=MIDDLE  ALT=\"y=3x%2B7\"   DISABLED_style= \"max-width:90%; height:auto;\" >), in the place of y in the second equation.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x%2B%283x%2B7%29=-9 ALIGN=MIDDLE  ALT=\"x%2B%283x%2B7%29=-9\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=4x%2B7=-9 ALIGN=MIDDLE  ALT=\"4x%2B7=-9\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=4x=-16 ALIGN=MIDDLE  ALT=\"4x=-16\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x=-4 ALIGN=MIDDLE  ALT=\"x=-4\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "Now that we have a value for x, we can substitute that back into either equation to find the value of y.\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x%2By=-9 ALIGN=MIDDLE  ALT=\"x%2By=-9\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-4%2By=-9 ALIGN=MIDDLE  ALT=\"-4%2By=-9\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=y=-5 ALIGN=MIDDLE  ALT=\"y=-5\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "Does this check?\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3%28-4%29-%28-5%29=-7 ALIGN=MIDDLE  ALT=\"3%28-4%29-%28-5%29=-7\"   DISABLED_style= \"max-width:90%; height:auto;\" >?<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-12%2B5=-7 ALIGN=MIDDLE  ALT=\"-12%2B5=-7\"   DISABLED_style= \"max-width:90%; height:auto;\" >, check\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-4%2B%28-5%29=-9 ALIGN=MIDDLE  ALT=\"-4%2B%28-5%29=-9\"   DISABLED_style= \"max-width:90%; height:auto;\" >, check\r<BR>\n" );
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document.write( "If you graphed these lines, you would see that the two lines intersect at the point (-4,-5).\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=graph%28400%2C400%2C-12%2C2%2C-12%2C2%2C3x%2B7%2C-x-9%29 ALIGN=MIDDLE  ALT=\"graph%28400%2C400%2C-12%2C2%2C-12%2C2%2C3x%2B7%2C-x-9%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( " </SPAN>\n" );
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