SAT Math Multiple Choice Practice Question 98: Answer and Explanation
The angle marked a in the drawing above measures
Correct Answer: E
E. The missing angle in the triangle must be 30°. And because a and this angle make a straight line (180°), a must be 150° (the difference of 180 - 30). In case you're interested, the great world of geometry has also come up with a rule for this sort of problem: The exterior angle of a triangle is always equal to the sum of the two remote interior angles.