Explanation for Question 12 From the Math (Calc) Section on the 2018 May Sat
Question 12 says in the figure above line L is parallel to line up. 2 If X is equal to 40, what is the measure of angle D F? 3 So we know that this angle is equal to 40 and that this angle 4 is equal to 40. So from that, 5 the first thing we can do is find the measure of angle D E 6 G. And that's because we know that this is a right angle and that 7 right angles are 90 degrees. So that tells us that 40 plus 8 we'll just call this angle. Y is equal to 90 degrees, 9 which means that Y is equal to 50 degrees. 10 So we know this is equal to 50 degrees. We also know that this 11 angle is equal to 90 degrees and that this angle is equal to 40 12 degrees, which means we can find this angle by adding 90 plus 40 to 13 get 130 and subtract from that from 180. 14 And we get 50 degrees. So we know that both of these two 15 angles are equal to 50 degrees, which means that angle Def is just 50 16 plus 50 or a hundred degrees, 17 which is answer choice.