document.write( "Question 584943: Mary is 21 years older than john in 12 years time Mary will be twice as old as John what age is Mary \n" ); document.write( "
Algebra.Com's Answer #373324 by Maths68(1474)\"\" \"About 
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Let
\n" ); document.write( "Present age of Mary = m
\n" ); document.write( "Present age of John = j\r
\n" ); document.write( "\n" ); document.write( "Given
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\n" ); document.write( "Mary is 21 years older than john
\n" ); document.write( "m=j+21.............(1)
\n" ); document.write( "In 12 years time
\n" ); document.write( "Mary will be = m+12
\n" ); document.write( "John will be = j+12
\n" ); document.write( "Then
\n" ); document.write( "Mary will be twice as old as John
\n" ); document.write( "m+12=2(j+12)
\n" ); document.write( "m+12=2j+24
\n" ); document.write( "m=2j+24-12
\n" ); document.write( "m=2j+12.............(2)
\n" ); document.write( "Put the value of m in (2)
\n" ); document.write( "j+21=2j+12
\n" ); document.write( "j-2j=12-21
\n" ); document.write( "-j=-9
\n" ); document.write( "cancel out (-)
\n" ); document.write( "j=9\r
\n" ); document.write( "\n" ); document.write( "Put the value of j in (1)
\n" ); document.write( "m=j+21.............(1)
\n" ); document.write( "m=9+21
\n" ); document.write( "m=30\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Present age of Mary = m = 30
\n" ); document.write( "Present age of John = j = 9
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