#### Answer

$\frac{10n-7}{n(n-1)}$

#### Work Step by Step

First, we find a common denominator. This, upon inspection, is found to be $n(n-1)$. Then, we add the two fractions using this common denominator:
$\frac{7}{n}+\frac{3}{n-1}$
=$\frac{7(n-1)+3(n)}{n(n-1)}$
=$\frac{7n-7+3n}{n(n-1)}$
=$\frac{10n-7}{n(n-1)}$