document.write( "Question 180998: 3. Walt made an extra $12,000 last year from a part-time job. He invested part of the money at 7% and the rest at 9%. He made a total of $970 in interest. How much was invested at 7%? \n" ); document.write( "

Algebra.Com's Answer #135672 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
Let $\"a\"$ = amount invested @ 7%
\n" ); document.write( "Let $\"b\"$ = amount invested @ 9%
\n" ); document.write( "given:
\n" ); document.write( "(1) $\".07a+%2B+.09b+=+970\"$
\n" ); document.write( "(2) $\"a+%2B+b+=+12000\"$
\n" ); document.write( "Multiply both sides of (2) by $\".07\"$
\n" ); document.write( "and subtract from (1)
\n" ); document.write( "(1) $\".07a+%2B+.09b+=+970\"$
\n" ); document.write( "(2) $\"-.07a+-+.07b+=+.07%2A12000\"$
\n" ); document.write( "And, subtracting:
\n" ); document.write( "(1) $\".07a+%2B+.09b+=+970\"$
\n" ); document.write( "(2) $\"-.07a+-+.07b+=+-840\"$
\n" ); document.write( " $\".02b+=+130\"$
\n" ); document.write( " $\"b+=+6500\"$
\n" ); document.write( "And, since
\n" ); document.write( "(2) $\"a+%2B+b+=+12000\"$
\n" ); document.write( " $\"a+=+12000+-+6500\"$
\n" ); document.write( " $\"a+=+5500\"$
\n" ); document.write( "$5500 was invested @ 7%
\n" ); document.write( "check:
\n" ); document.write( "(1) $\".07a+%2B+.09b+=+970\"$
\n" ); document.write( " $\".07%2A5500+%2B+.09%2A6500+=+970\"$
\n" ); document.write( " $\"385+%2B+585+=+970\"$
\n" ); document.write( " $\"970+=+970\"$
\n" ); document.write( "OK \n" ); document.write( "

\n" );