Answer: B) 42 + x = 90
Explanation:
A complementary angle always equals 90 degrees. So, with that information, all you have to do is list the measurement of b as x and create an equation. Knowing that the measurement of angle a is 42 degrees, we can now find an equation. So, we would take the measurement of angle a, 42 degrees, and add the measurement of angle b, listed as x, which should equal 90 degrees.