These two angles are vertical angles. Vertical angles are equal to each other
Step 1: Set the angles equal to each other
3x + 50 = 6x - 10
Step 2: Solve for x
3x + (50 + 10) = 6x + (-10 + 10)
3x + 60 = 6x + 0
(3x-3x) + 60 = 6x - 3x
0 + 60 = 3x
60/3 = 3x / 3
x = 20
Hope this helped!