Answer
$ \frac{3q+7p}{pq}$
Work Step by Step
We want a common denominator before we add. The least common multiple (LCM) of these denominators is "pq", so the left term should be multiplied by q/q, and the right term should be multiplied by p/p.
$\frac{3}{p} + \frac{7}{q} = \frac{3}{p}*\frac{q}{q} + \frac{7}{q}*\frac{p}{p} = \frac{3q}{pq} + \frac{7p}{pq} = \frac{3q+7p}{pq}$
