document.write( "Question 1051724: Mary’s father is four times as old as Mary. Five years ago, he was seven times as old. How old is each now? \n" ); document.write( "

Algebra.Com's Answer #667211 by josmiceli(19441) $\"\"$ $\"About$

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Let $\"+a+\"$ = Mary's age now
\n" ); document.write( "Let $\"+b+\"$ = her father's age now
\n" ); document.write( "---------------------------------
\n" ); document.write( "(1) $\"+b+=+4a+\"$
\n" ); document.write( "(2) $\"+b+-+5+=+7%2A%28+a+-+5+%29+\"$
\n" ); document.write( "---------------------------
\n" ); document.write( "Substitute (1) into (2)
\n" ); document.write( "(2) $\"+4a+-+5+=+7%2A%28+a+-+5+%29+\"$
\n" ); document.write( "(2) $\"+4a+-+5+=+7a+-+35+\"$
\n" ); document.write( "(2) $\"+3a+=+35+-+5+\"$
\n" ); document.write( "(2) $\"+3a+=+30+\"$
\n" ); document.write( "(2) $\"+a+=+10+\"$
\n" ); document.write( "and
\n" ); document.write( "(1) $\"+b+=+4a+\"$
\n" ); document.write( "(1) $\"+b+=+4%2A10+\"$
\n" ); document.write( "(1) $\"+b+=+40+\"$
\n" ); document.write( "----------------
\n" ); document.write( "Mary is 10
\n" ); document.write( "Her father is 40
\n" ); document.write( "----------------
\n" ); document.write( "check:
\n" ); document.write( "(2) $\"+b+-+5+=+7%2A%28+a+-+5+%29+\"$
\n" ); document.write( "(2) $\"+40+-+5+=+7%2A%28+10+-+5+%29+\"$
\n" ); document.write( "(2) $\"+35+=+7%2A5+\"$
\n" ); document.write( "(2) $\"+35+=+35+\"$
\n" ); document.write( "OK \n" ); document.write( "

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