7) 2 1/4 : (-3 3/5)

7) $$2 \frac{1}{4} : (-3 \frac{3}{5}) = \frac{9}{4} : (- \frac{18}{5} ) = \frac{9}{4} \cdot (- \frac{5}{18}) = - \frac{9}{4} \cdot \frac{5}{18} = - \frac{1}{4} \cdot \frac{5}{2} = - \frac{5}{8}$$.

Ответ: $$- \frac{5}{8}$$