SAT Question e89f63bf: Lines, Angles, and Triangles answer and explanation with Desmos solution

Choice C is correct. It’s given that the sum of the measures of two angles in a triangle is $64^{\circ }$. The sum of the measures of all three angles in a triangle is $180^{\circ }$. It follows that the measure of the third angle is the difference between $180^{\circ }$ and $64^{\circ }$, or $180-64$, which is $116^{\circ }$. Therefore, the measure of the third angle is $116^{\circ }$.