document.write( "Question 1102620: Four years ago, the father's age was three times the age of his son., The total of the ages of the father and the son after four years, will be 64 years. What is the father's age at present ? \n" ); document.write( "
Algebra.Com's Answer #717331 by josmiceli(19441)\"\" \"About 
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Let \"+a+\" = the son's age now
\n" ); document.write( "Let \"+b+\" = the father's age now
\n" ); document.write( "---------------------------------
\n" ); document.write( "(1) \"+b+-+4+=+3%2A%28+a+-+4+%29+\"
\n" ); document.write( "(2) \"+%28+a+%2B+4+%29+%2B+%28+b+%2B+4+%29+=+64+\"
\n" ); document.write( "--------------------------------
\n" ); document.write( "(1) \"+b+-+4+=+3a+-+12+\"
\n" ); document.write( "(1) \"+3a+-+b+=+8+\"
\n" ); document.write( "and
\n" ); document.write( "(2) \"+a+%2B+b+%2B+8+=+64+\"
\n" ); document.write( "(2) \"+a+%2B+b+=+56+\"
\n" ); document.write( "-------------------------
\n" ); document.write( "Add (1) and (2)
\n" ); document.write( "(1) \"+3a+-+b+=+8+\"
\n" ); document.write( "(2) \"+a+%2B+b+=+56+\"
\n" ); document.write( "----------------------
\n" ); document.write( "\"+4a+=+64+\"
\n" ); document.write( "\"+a+=+16+\"
\n" ); document.write( "and
\n" ); document.write( "(2) \"+16+%2B+b+=+56+\"
\n" ); document.write( "(2) \"+b+=+40+\"
\n" ); document.write( "------------------------
\n" ); document.write( "The father is 40 at present
\n" ); document.write( "------------------------
\n" ); document.write( "check:
\n" ); document.write( "(1) \"+b+-+4+=+3%2A%28+a+-+4+%29+\"
\n" ); document.write( "(1) \"+40+-+4+=+3%2A%28+16+-+4+%29+\"
\n" ); document.write( "(1) \"+36+=+3%2A12+\"
\n" ); document.write( "(1) \"+36+=+36+\"
\n" ); document.write( "and
\n" ); document.write( "(2) \"+%28+a+%2B+4+%29+%2B+%28+b+%2B+4+%29+=+64+\"
\n" ); document.write( "(2) \"+20+%2B+44+=+64+\"
\n" ); document.write( "(2) \"+64+=+64+\"
\n" ); document.write( "OK
\n" ); document.write( "
\n" );