document.write( "Question 85098: Solve the system by substitution.
\n" ); document.write( " 3x – y = –7
\n" ); document.write( " x + y = –9
\n" ); document.write( " \n" ); document.write( "
Algebra.Com's Answer #61331 by nateobot(1)\"\" \"About 
You can put this solution on YOUR website!
3x – y = –7
\n" ); document.write( "x + y = –9
\n" ); document.write( "y = -9 -x
\n" ); document.write( "

\n" ); document.write( "3x - (-9 - x) = -7
\n" ); document.write( "3x + 9 + x = -7
\n" ); document.write( "4x + 9 = -7
\n" ); document.write( "4x = -16
\n" ); document.write( "x = -4
\n" ); document.write( "

\n" ); document.write( "-4 + y = -9
\n" ); document.write( "y = -5
\n" ); document.write( "

\n" ); document.write( "Proof:
\n" ); document.write( "

\n" ); document.write( "3(-4) - (-5) = -7
\n" ); document.write( "-12 + 5 = -7
\n" ); document.write( "-7 = -7
\n" ); document.write( "

\n" ); document.write( "-4 + (-5) = -9
\n" ); document.write( "-9 = -9 \n" ); document.write( "
\n" );