Answer
See below.
Work Step by Step
According to the exercise $y=\frac{a}{x}$ for some constant $a$. Then plugging in the values given: $\frac{5}{8}=\frac{a}{\frac{3}{4}}\\a=\frac{15}{32}$,
hence $y=\frac{15}{32}\frac{1}{x}$.
Hence here: $y=\frac{15}{32}\frac{1}{4}=\frac{15}{128}$.
