document.write( "Question 332797: John, twelve years old, is three times as old as his brother. How old will John be when he is twice as old as his brother? \n" ); document.write( "
Algebra.Com's Answer #238469 by jrfrunner(365)\"\" \"About 
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John, twelve years old, is three times as old as his brother. How old will John be when he is twice as old as his brother?
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\n" ); document.write( "\n" ); document.write( "Let John's age = J = 12
\n" ); document.write( "Let John's brother's age = B
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\n" ); document.write( "TODAY
\n" ); document.write( "J = 3*B is given
\n" ); document.write( "since J=12, then B=4
\n" ); document.write( "Today John's brother is 4 years old
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\n" ); document.write( "future: X years away
\n" ); document.write( "J+X is John's age x years away
\n" ); document.write( "B+X is John's brother's age x years away
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\n" ); document.write( "How old will John be when he is twice as old as his brother?
\n" ); document.write( "we want to find J+X
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\n" ); document.write( "\n" ); document.write( "J+X=2*(B+X) we know today J=12, B=4 so substitute and solve for X\r
\n" ); document.write( "\n" ); document.write( "12+x=2*(4+X)
\n" ); document.write( "12+x=8+2x
\n" ); document.write( "4=x (four years in the future the above relationship will hold true\r
\n" ); document.write( "\n" ); document.write( "so J+X = 12+4=16\r
\n" ); document.write( "\n" ); document.write( "When John is 16 he will be twice his brother's age (B+X) = 4+4=8
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