document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=395422>Question 395422</A>: <I><SPAN STYLE=\"word-break: break-all;\"> a salesperson purchased a car that avg 25mpg in the city and 40 mpg on highway.  A recent sales trip that covered 1800 miles required 51 gal of gas.  Assuming the advertised mileage estimates were correct, how many  miles were driven in the city? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #280615 by </B><A HREF=/tutors/aboutme.mpl?userid=jrfrunner><B>jrfrunner(365)</B></A><img src=\"/images/stars/stars-10.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=jrfrunner><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=jrfrunner><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=280615\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> you have two unknowns:   C=gallons used in city driving and H=gallons used in highway driving<BR>\n" );
document.write( "so you will need two equations to solve the two unknowns<BR>\n" );
document.write( "--<BR>\n" );
document.write( "eq1  gallons used:    C+H=51 <BR>\n" );
document.write( "eq2  miles driven: 25*C+40*H=1800<BR>\n" );
document.write( "-<BR>\n" );
document.write( "solve eq1 for H:   H=51-C and substitute in eq2<BR>\n" );
document.write( "25*C+40*(51-C)=1800  solve for C<BR>\n" );
document.write( "25C-40C+2040=1800 <BR>\n" );
document.write( "2040-1800=15C<BR>\n" );
document.write( "C=240/15=16gallons used<BR>\n" );
document.write( "--<BR>\n" );
document.write( "they want to know how many miles were driven in the city\r<BR>\n" );
document.write( "\n" );
document.write( "25*C=25*16=400 miles </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );