Let's call \(a\) the number of hours it takes for A to fill the pool and \(b\) the number of hours it takes for B to fill the pool.
We have \(a=b-3\) and \(\frac{2}a+\frac{2}b=1\) hence \(\frac{2}{b-3}+\frac{2}b=1\Leftrightarrow b^2-7b+6=0\Leftrightarrow b=6\text{ or }b=-1\) hence \(b=6\) and thus \(a=3\).
\(\boxed{b=6,a=3}\)
