$$\left(\frac{3}{8} + \left(\frac{1}{2}\right)^2 + 1\frac{1}{4}\right) : \frac{5}{3}$$
$$\left(\frac{3}{8} + \frac{1}{4} + \frac{5}{4}\right) : \frac{5}{3} = \left(\frac{3}{8} + \frac{2}{8} + \frac{10}{8}\right) : \frac{5}{3} = \frac{15}{8} : \frac{5}{3} = \frac{15}{8} \cdot \frac{3}{5} = \frac{45}{40} = \frac{9}{8}$$
Ответ: $$\frac{9}{8}$$