#### Answer

$\frac{2(2m+n)}{m+n}$

#### Work Step by Step

Step 1: $\frac{\frac{m}{3}+\frac{n}{6}}{\frac{m+n}{12}}$
Step 2: $\frac{\frac{m\times2}{3\times2}+\frac{n\times1}{6\times1}}{\frac{m+n}{12}}$
Step 3: $\frac{\frac{2m}{6}+\frac{n}{6}}{\frac{m+n}{12}}$
Step 4$\frac{\frac{2m+n}{6}}{\frac{m+n}{12}}$
Step 5:$\frac{2m+n}{6}\div\frac{m+n}{12}$
Step 6: $\frac{2m+n}{6}\times\frac{12}{m+n}$
Step 7: $\frac{2(2m+n)}{m+n}$