document.write( "Question 72319: Solve the following 2 x 2 systems using substitutions\r
\n" ); document.write( "\n" ); document.write( "3x - y = 5
\n" ); document.write( "6x + 5y =-18 \n" ); document.write( "

Algebra.Com's Answer #51709 by elima(1433) $\"\"$ $\"About$

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3x - y = 5
\n" ); document.write( "6x + 5y =-18
\n" ); document.write( "Take the first equation and change it around so we have;
\n" ); document.write( "-y = 5 - 3x
\n" ); document.write( "y = 3x - 5
\n" ); document.write( "Now plug that into the second equation for y;
\n" ); document.write( "6x + 5(3x - 5)= -18
\n" ); document.write( "6x + 15x - 25 = -18
\n" ); document.write( "21x = -18 +25
\n" ); document.write( "21x = 7
\n" ); document.write( "x = $\"7%2F21\"$ = $\"1%2F3\"$
\n" ); document.write( "Now plug that into the equation for x;
\n" ); document.write( "3({{1/3}}}) - y = 5
\n" ); document.write( " $\"3%2F3\"$ - y = 5
\n" ); document.write( "1 - y =5
\n" ); document.write( "-y = 5-1
\n" ); document.write( "-y = 4
\n" ); document.write( "y = -4
\n" ); document.write( ":) \n" ); document.write( "

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