SAT Question 74d8b897: Circles answer and explanation with Desmos solution

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 $\left(\frac{9\pi }{20}\text{radians}\right)\left(\frac{180\text{degrees}}{\pi \text{radians}}\right)$, which is equivalent to $81$ degrees.