How do I start the equation?

Answer:
Step-by-step explanation:
Well they add up to a straight line which would be 180 degrees. That means 40, 6x+2 and 90 all add up to 180
40 + 90 + 6x + 2 = 180
Answer:
x = 8
Step-by-step explanation:
40 + 6x + 2 = 90° because these angles are complementary
6x = 90 - 42
6x = 48 divide both sides by 6
x = 8