Circles SAT question

The correct answer is $81$. The measure of an angle, in degrees, can be found by multiplying its measure, in radians, by $\frac{180\text{degrees}}{\pi \text{radians}}$. Multiplying the given angle measure, $\frac{9\pi }{20}$ radians, by $\frac{180\text{degrees}}{\pi \text{radians}}$ yields $(\frac{9\pi }{20}\text{radians})(\frac{180\text{degrees}}{\pi \text{radians}})$, which is equivalent to $81$ degrees.