document.write( "Question 243956: Please solve Using Substitution:
\n" ); document.write( " $\"7s%2B5t=13\"$
\n" ); document.write( " $\"3t-s=-13\"$ \n" ); document.write( "

Algebra.Com's Answer #178608 by richwmiller(17219) $\"\"$ $\"About$

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Please solve Using Substitution:
\n" ); document.write( "7s+5t=13
\n" ); document.write( "3t-s=-13
\n" ); document.write( "solve second for s
\n" ); document.write( "add 13 and s to both sides
\n" ); document.write( "3t+13=s
\n" ); document.write( "substitute s into first
\n" ); document.write( "7* (3t+13)+5t=13
\n" ); document.write( "21t+7*13+5t=13
\n" ); document.write( "combine
\n" ); document.write( "26t+7*13=13
\n" ); document.write( "divide by 13
\n" ); document.write( "2t+7=1
\n" ); document.write( "subtract 7 from both sides
\n" ); document.write( "2t=-6
\n" ); document.write( "t=-3
\n" ); document.write( "substitute t into second equation
\n" ); document.write( "why second?
\n" ); document.write( "it is easier to multiply and divide
\n" ); document.write( "3*(-3)-s=-13
\n" ); document.write( "-9-s=-13\r
\n" ); document.write( "\n" ); document.write( "multiply both sides by -1\r
\n" ); document.write( "\n" ); document.write( "9+S=13
\n" ); document.write( "s=4
\n" ); document.write( "and t=-3
\n" ); document.write( "check
\n" ); document.write( "7s+5t=13
\n" ); document.write( "7*4+5*(-3)=13
\n" ); document.write( "28-15=13
\n" ); document.write( "13=13
\n" ); document.write( "ok \n" ); document.write( "

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