document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=147686>Question 147686</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Christi's mother gave her $9.00 to buy 10 cent and 15 cent stamps. Christi returned with $1.75 in change and a total of 60 stamps. How many of each kind of stamp did she buy? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #108051 by </B><A HREF=/tutors/aboutme.mpl?userid=mangopeeler07><B>mangopeeler07(462)</B></A><img src=\"/images/stars/stars-10.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=mangopeeler07><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/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=108051\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> -----With two variables:   # of 10 cent stamps is x. # of 15 cent stamps is y.  You have the prices of the stamps and the sum of the price of 60 stamps.  So first set up an equation <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x%2By=60 ALIGN=MIDDLE  ALT=\"x%2By=60\"   DISABLED_style= \"max-width:90%; height:auto;\" >. Then set up <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=10x%2B15y=725 ALIGN=MIDDLE  ALT=\"10x%2B15y=725\"   DISABLED_style= \"max-width:90%; height:auto;\" >.  Then in the first equation solve for x.  You should get <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x=60-y ALIGN=MIDDLE  ALT=\"x=60-y\"   DISABLED_style= \"max-width:90%; height:auto;\" >. Plug that in the second equation and get <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=10%2860-y%29%2B15y=725 ALIGN=MIDDLE  ALT=\"10%2860-y%29%2B15y=725\"   DISABLED_style= \"max-width:90%; height:auto;\" >. Distribute the ten and get <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=600-10y%2B15y=725 ALIGN=MIDDLE  ALT=\"600-10y%2B15y=725\"   DISABLED_style= \"max-width:90%; height:auto;\" >.  Combine like terms <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=600%2B5y=725 ALIGN=MIDDLE  ALT=\"600%2B5y=725\"   DISABLED_style= \"max-width:90%; height:auto;\" >.  Subtract 600 from both sides and get <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=5y=125 ALIGN=MIDDLE  ALT=\"5y=125\"   DISABLED_style= \"max-width:90%; height:auto;\" >.  Then divide by five and <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=y=25 ALIGN=MIDDLE  ALT=\"y=25\"   DISABLED_style= \"max-width:90%; height:auto;\" >.  Then plug in y in the original equation and get <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x=35 ALIGN=MIDDLE  ALT=\"x=35\"   DISABLED_style= \"max-width:90%; height:auto;\" >.  So she bought 35 10cent stamps and 25 15 cent stamps.\r<BR>\n" );
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document.write( "-----With one variable:   Also, you could start out with <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=10x%2B15%2860-x%29=725 ALIGN=MIDDLE  ALT=\"10x%2B15%2860-x%29=725\"   DISABLED_style= \"max-width:90%; height:auto;\" > since you know the sum to be 60.  Then distribute and get <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=10x%2B900-15x=725 ALIGN=MIDDLE  ALT=\"10x%2B900-15x=725\"   DISABLED_style= \"max-width:90%; height:auto;\" >. Combine like terms and get <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-5x%2B900=725 ALIGN=MIDDLE  ALT=\"-5x%2B900=725\"   DISABLED_style= \"max-width:90%; height:auto;\" >.  Subtract 900 from each side and get <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-5x=175 ALIGN=MIDDLE  ALT=\"-5x=175\"   DISABLED_style= \"max-width:90%; height:auto;\" >.  Divide by -5 and get x=-35.  Now, you can't buy a negative amount of stamps, so make 35 positive. <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x=35 ALIGN=MIDDLE  ALT=\"x=35\"   DISABLED_style= \"max-width:90%; height:auto;\" >.  Then plug x into the original equation and get <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=y=25 ALIGN=MIDDLE  ALT=\"y=25\"   DISABLED_style= \"max-width:90%; height:auto;\" >.  So she bought 35 10cent stamps and 25 15 cent stamps.<BR>\n" );
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