Answer
$\dfrac{7}{32}$
Work Step by Step
To write a percent as a fraction, drop the % symbol and multiply by $\dfrac{1}{100}$.
$21\dfrac{7}{8}\% \rightarrow 21\dfrac{7}{8} \rightarrow \dfrac{\frac{175}{8}}{100} = \dfrac{175}{800} = \dfrac{7}{32}$