Answer:
B) 78
Explanation:
The two lines we are going to want to pay attention to for this problem are line S and line Q. ALWAYS remember that a line adds up to 180 degrees. This means that when we find x, we know that 57 + x + another number equals 180, because they are all angles on line S.
So, all we need to do is find this "other number". We can do this by looking at line Q. Again, since all lines add up to 180, the other angle on line Q must be 45 degrees, because 135 and 45 add up to 180. And now we know our "other number", its 45!
But how do we know the "other number" is 45? Well, its because the lines that creat these angles are both parallel (line S and line R) and have the same line crossing them (line Q).
Now we can finish our problem. We should get 57 + x + 45 = 180. This then gives us x = 78.