Question 1095164
.
<pre>
MENTAL solution:


1.  "Two years ago the sum of their ages was 17."  ====>  the sum of their ages now is 17+4 = 21.



2.  "Kevin is two times as old as Bob. " and the sum of their ages now is 21  ====>  Kevin is 14 years old; Bob is 7 years old.
</pre>

Solved.