SOLUTION: John is 6 years older than his brother. He will be twice as old as his brother in 4 years. How old is John now.

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Question 698270: John is 6 years older than his brother. He will be twice as old as his brother in 4 years. How old is John now.



Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +a+ = John's age now
Let +b+ = his Brother's age now
given:
(1) +a+=+b+%2B+6+
(2) +a+%2B+4+=+2%2A%28+b+%2B+4+%29+
-----------------------
Substitute (1) into (2)
(2) +b+%2B+6+%2B+4+=+2%2A%28+b+%2B+4+%29+
(2) +b+%2B+10+=+2b+%2B+8+
(2) +b+=+10+-+8+
(2) +b+=+2+
and
(1) +a+=+b+%2B+6+
(1) +a+=+2+%2B+6+
(1) +a+=+8+
John is 8 yrs old
check:
(2) +a+%2B+4+=+2%2A%28+b+%2B+4+%29+
(2) +8+%2B+4+=+2%2A%28+2+%2B+4+%29+
(2) +12+=+2%2A6+
(2) +12+=+12+
OK