Question 979859
The ages of Ravi and Raja are in the ratio 5:12.
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So there is some positive integer k such that Ravi is 5k and Raja is 12k
[so that {{{(5k)/(12k)}}}{{{""=""}}}{{{5/12}}}.]
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After 6 years the ratio of their ages will be 8:15. 
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After 6 years Ravi will be 5k+6 and Raja will be 12k+6, then 

{{{(5k+6)/(12k+6)}}}{{{""=""}}}{{{8/15}}}

Solve that equation for k.  Then find their ages 5k and 12k.
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What is the different between their ages?
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Subtract Raja's age MINUS Ravi's age.

Edwin</pre>