Answer
$q-p$
Work Step by Step
Multiply $\frac{pq}{pq}$ to the expression, we have:
$\frac{p^{-1}-q^{-1}}{(pq)^{-1}}=\frac{p^{-1}-q^{-1}}{(pq)^{-1}}\cdot\frac{pq}{pq}=\frac{q-p}{1}=q-p$
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