document.write( "Question 1150389: Twelve years ago my father was twice as old as I was, and three years ago our combined age was 108. How old is my father now? \n" ); document.write( "

Algebra.Com's Answer #771779 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
Let $\"+a+\"$ = my father's age now
\n" ); document.write( "Let $\"+b+\"$ = my age now
\n" ); document.write( "(1) $\"+a+-+12+=+2%2A%28+b+-+12+%29+\"$
\n" ); document.write( "(2) $\"+%28+a+-+3+%29+%2B+%28+b+-+3+%29+=+108+\"$
\n" ); document.write( "----------------------------------------
\n" ); document.write( "(1) $\"+a+-+12+=+2b+-+24+\"$
\n" ); document.write( "(1) $\"+-a+%2B+2b+=+12+\"$
\n" ); document.write( "and
\n" ); document.write( "(2) $\"+a+%2B+b+-+6+=+108+\"$
\n" ); document.write( "(2) $\"+a+%2B+b+=+114+\"$
\n" ); document.write( "-------------------------------
\n" ); document.write( "add (1) and (2)
\n" ); document.write( "(1) $\"+-a+%2B+2b+=+12+\"$
\n" ); document.write( "(2) $\"+a+%2B+b+=+114+\"$
\n" ); document.write( "---------------------------
\n" ); document.write( " $\"+3b+=+126+\"$
\n" ); document.write( " $\"+b+=+42+\"$
\n" ); document.write( "and
\n" ); document.write( "(2) $\"+a+%2B+42+=+114+\"$
\n" ); document.write( "(2) $\"+a+=+72+\"$
\n" ); document.write( "------------------------
\n" ); document.write( "My father is 72 now
\n" ); document.write( "------------------------
\n" ); document.write( "check:
\n" ); document.write( "(1) $\"+a+-+12+=+2%2A%28+b+-+12+%29+\"$
\n" ); document.write( "(1) $\"+72+-+12+=+2%2A%28+42+-+12+%29+\"$
\n" ); document.write( "(1) $\"+60+=+2%2A30+\"$
\n" ); document.write( "(1) $\"+60+=+60+\"$
\n" ); document.write( "and
\n" ); document.write( "(2) $\"+%28+a+-+3+%29+%2B+%28+b+-+3+%29+=+108+\"$
\n" ); document.write( "(2) $\"+%28+72+-+3+%29+%2B+%28+42+-+3+%29+=+108+\"$
\n" ); document.write( "(2) $\"+69+%2B+39+=+108+\"$
\n" ); document.write( "(2) $\"+108+=+108+\"$
\n" ); document.write( "OK \n" ); document.write( "

\n" );