## Elementary Technical Mathematics

$$\frac{1}{12}.$$
We simplify by removing the parenthesis and add the terms as follows: $$\frac{-3}{16}\div \left( -2\frac{1}{4} \right)= \frac{-3}{16}\div \frac{-9}{4}\\ =\frac{-3}{16} \cdot \frac{4}{-9}=\frac{1}{12}.$$