document.write( "Question 173665: How do you solve by the addition-or-subtraction method.
\n" ); document.write( "12a-5b=18
\n" ); document.write( "15a-5b=30 \n" ); document.write( "

Algebra.Com's Answer #128521 by jojo14344(1513) $\"\"$ $\"About$

You can put this solution on YOUR website!

\n" ); document.write( " $\"12a-5b=18\"$ ----> $\"12a-5b-18\"$ , EQN 1
\n" ); document.write( " $\"15a-5b=30\"$ ----> $\"15a-5b-30=0\"$ , EQN 2
\n" ); document.write( "Subtract EQN 1 to EQN 2:
\n" ); document.write( "where-----> $\"system%2812a-5b-18=0%2C-15a%2B5b%2B30=0%2Chighlight%28-3a%2B12=0%29%29\"$ --> see EQN 2, change \"signs\" when subtacting right?
\n" ); document.write( "Continuing the \"highlighted\" eqn:
\n" ); document.write( " $\"-3a=-12\"$ -----> $\"cross%28-3%29a%2Fcross%28-3%29=cross%28-12%294%2Fcross%28-3%29\"$
\n" ); document.write( " $\"highlight%28a=4%29\"$
\n" ); document.write( "Go back EQN 1:
\n" ); document.write( " $\"12%2A4-5b=18\"$
\n" ); document.write( " $\"48-18=5b\"$ ---> $\"30=5b\"$ ---> $\"cross%2830%296%2Fcross%285%29=cross%285%29b%2Fcross%285%29\"$
\n" ); document.write( " $\"highlight%28b=6%29\"$
\n" ); document.write( "Check go back EQN 2:
\n" ); document.write( " $\"15%2A4-5%2A6-30=0\"$
\n" ); document.write( " $\"60-30-30=0\"$
\n" ); document.write( " $\"0=0\"$
\n" ); document.write( "Thank you,
\n" ); document.write( "Jojo\r
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

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