Answer:
36
Explanation:
This is a Linear Pair. Adjacent (next to) angles that form a straight line. A good rule of thumb for 90% of Geometry, angle relationships are usually either supplementary or congruent. In this case, since they together form a straight line, they are supplementary.
x + 4x = 180
5x = 180
180/5 = 36
If you plug these numbers in, you have a 36 degree angle and a 144 degree angle (sum of 180). Easy way to check your work if ever unsure.