the ages of two brothers are 11 and 8 in how many years time will the broduct of their ages be 208 ?
(11+x)(8+x) = 208
Now just expand and solve for x
or, look for factors of 208 that differ by 3. Since they are almost equal, they will be near √208 = 14.4
So, I'd guess 16*13 = 208