[Video] Q5: In the figure above, lines l and m are parallel, y = 20, and z = 60. what is the value of x ?

Explanation for Question 5 From the Math (Calc) Section on the Official Sat Practice Test 8

So question five gives us two triangles, 2 which are created by two parallel lines lines, 3 L and line M and there tell us that Y is equal to 20 4 and Z is equal to 60, and then they want to know what is 5 the value of X, right. 6 We see the X as part of a little triangle up here. 7 And so if we add X plus 60 plus here, 8 we'll call this a right. We don't know that angle, 9 but if we add all three of those together, 10 we would get 180 degrees because all the angles in a triangle add up 11 to 180 degrees. And so now if we look at this, 12 we can ask ourselves, okay, how do I find the measure of angle a 13 and I can find the measure of angle a by using the information given 14 to me about the parallel lines, 15 what we notice about a and why is that they're actually corresponding angles, 16 right? Because why would be the upper right-hand corner of this 17 little intersection? And then a would be the upper right-hand corner of the second 18 intersection. So if Y is the same as a, 19 then a is 20, and if we subtract 20 and 60 from 180, 20 we get a hundred. So our correct answer is B.