document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1050529>Question 1050529</A>: <I><SPAN STYLE=\"word-break: break-all;\"> During one month, a homeowner used 300 units of electricity and 130 units of gas for a total cost of $110.30. The next month, 220 units of electricity and 250 units of gas were used for a total cost of $97.90. Find the cost per unit of gas. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #666098 by </B><A HREF=/tutors/aboutme.mpl?userid=advanced_Learner><B>advanced_Learner(501)</B></A><img src=\"/images/stars/stars-10.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=advanced_Learner><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=advanced_Learner><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=666098\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> 300x+130y=110.30<BR>\n" );
document.write( "220x+250y=97.90\r<BR>\n" );
document.write( "\n" );
document.write( "<TABLE  BORDER=1>\n" );
document.write( "\n" );
document.write( " <TR><TD  ALIGN=MIDDLE>Solved by <A  rel=nofollow HREF=http://wiki.algebra.com/index.php/Tutoring_-_pluggable_solvers>pluggable</A> solver: <A  rel=nofollow HREF=linear_substitution.solver>SOLVE linear system by SUBSTITUTION</A></TD></TR>\n" );
document.write( "<TR><TD  ALIGN=LEFT>Solve:<BR>\n" );
document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+system%28+%0D%0A++++300%5Cx+%2B+130%5Cy+=+110.3%2C%0D%0A++++220%5Cx+%2B+250%5Cy+=+97.9+%29%0D%0A++ ALIGN=MIDDLE   DISABLED_style= \"max-width:90%; height:auto;\" >We'll use substitution. After moving 130*y to the right, we get:<BR>\n" );
document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=300%2Ax+=+110.3+-+130%2Ay ALIGN=MIDDLE  ALT=\"300%2Ax+=+110.3+-+130%2Ay\"   DISABLED_style= \"max-width:90%; height:auto;\" >, or <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x+=+110.3%2F300+-+130%2Ay%2F300 ALIGN=MIDDLE  ALT=\"x+=+110.3%2F300+-+130%2Ay%2F300\"   DISABLED_style= \"max-width:90%; height:auto;\" >. Substitute that<BR>\n" );
document.write( "  into another equation:<BR>\n" );
document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=220%2A%28110.3%2F300+-+130%2Ay%2F300%29+%2B+250%5Cy+=+97.9 ALIGN=MIDDLE  ALT=\"220%2A%28110.3%2F300+-+130%2Ay%2F300%29+%2B+250%5Cy+=+97.9\"   DISABLED_style= \"max-width:90%; height:auto;\" > and simplify: So, we know that y=0.11. Since <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x+=+110.3%2F300+-+130%2Ay%2F300 ALIGN=MIDDLE  ALT=\"x+=+110.3%2F300+-+130%2Ay%2F300\"   DISABLED_style= \"max-width:90%; height:auto;\" >, x=0.32.<BR>\n" );
document.write( "  <BR>\n" );
document.write( "  Answer: <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=system%28+x=0.32%2C+y=0.11+%29 ALIGN=MIDDLE  ALT=\"system%28+x=0.32%2C+y=0.11+%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >.<BR>\n" );
document.write( "  </TD></TR>\n" );
document.write( "</TABLE>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );