How would I find this? Would I do 90-40 and then get 50 or would I have to do 90-50 to get x?

Answer:
x = 50
Step-by-step explanation:
The sum of the 3 angles in a triangle = 180°
subtract the sum of the 2 given angles from 180 for x
x = 180 - (90 + 40) = 180 - 130 = 50