document.write( "Question 77068: Solve the system by substitution.
\n" ); document.write( " x + 3y = –8
\n" ); document.write( " 5x + 2y = 12
\n" ); document.write( " \n" ); document.write( "

Algebra.Com's Answer #55247 by tutorcecilia(2152) $\"\"$ $\"About$

You can put this solution on YOUR website!
x + 3y = –8 [pick one of the equations and solve for one of the variables]
\n" ); document.write( "x+3y=-8
\n" ); document.write( "x=-3y-8
\n" ); document.write( ".\r
\n" ); document.write( "\n" ); document.write( "5x + 2y = 12
\n" ); document.write( "5(-3y-8)+2y=12[plug the first equation into the second equation and solve for y]
\n" ); document.write( "-15y-40+2y=12
\n" ); document.write( "-13y=40+12
\n" ); document.write( "-13y=52
\n" ); document.write( "y=-4
\n" ); document.write( ".
\n" ); document.write( "Plug y=-4 into either equation and solve for the x-term.
\n" ); document.write( "5x+2y=12
\n" ); document.write( "5x+2(-4)=12
\n" ); document.write( "5x-8=12
\n" ); document.write( "5x=8+12
\n" ); document.write( "5x=20
\n" ); document.write( "x=4
\n" ); document.write( ".
\n" ); document.write( "checking:
\n" ); document.write( "5(4)+2(-4)=12
\n" ); document.write( "20-8=12
\n" ); document.write( "12=12 [checks out]\r
\n" ); document.write( "\n" ); document.write( "or
\n" ); document.write( "x + 3y = –8
\n" ); document.write( "(4)+3(-4)=-8
\n" ); document.write( "4-12=-8
\n" ); document.write( "-8=-8 [also checks out] \n" ); document.write( "

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