document.write( "Question 757467: Jack is twice as old as Jill. If 4 years ago Jack’s age was thrice as Jill’s. Find their present age. \n" ); document.write( "

Algebra.Com's Answer #460835 by josmiceli(19441) $\"\"$ $\"About$

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Let $\"+a+\"$ = Jack's age now
\n" ); document.write( "Let $\"+b+\"$ = Jill's age now
\n" ); document.write( "given:
\n" ); document.write( "(1) $\"+a+=+2b+\"$
\n" ); document.write( "(2) $\"++a+-+4+=+3%2A%28+b+-+4+%29+\"$
\n" ); document.write( "-----------------
\n" ); document.write( "By substitution,
\n" ); document.write( "(2) $\"+2b+-+4+=+3b+-+12+\"$
\n" ); document.write( "(2) $\"+b+=+12+-+4+\"$
\n" ); document.write( "(2) $\"+b+=+8+\"$
\n" ); document.write( "and, since
\n" ); document.write( "(1) $\"+a+=+2b+\"$
\n" ); document.write( "(1) $\"+a+=+2%2A8+\"$
\n" ); document.write( "(1) $\"+a+=+16+\"$
\n" ); document.write( "Jack is 16
\n" ); document.write( "Jill is 8
\n" ); document.write( "----------
\n" ); document.write( "check:
\n" ); document.write( "(2) $\"++a+-+4+=+3%2A%28+b+-+4+%29+\"$
\n" ); document.write( "(2) $\"++16+-+4+=+3%2A%28+8+-+4+%29+\"$
\n" ); document.write( "(2) $\"+12+=+3%2A4+\"$
\n" ); document.write( "(2) $\"+12+=+12+\"$
\n" ); document.write( "OK
\n" ); document.write( " \n" ); document.write( "

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