Answer:

Explanation:
We are given two angles, which together, have a sum of 90°. We call these complementary angles. The angle ∠EAF is the complement of angle ∠FAB and vice versa.
Therefore, because they sum up to be 90°, we can simply add the angles together and solve for x this way.

The variable x equals 10. We can go even further to check and verify that this is correct by substituting our original value for x into the equation.

90 does in fact equal 90, so your final answer is x = 10°.
Hope this helps! :)