Answer:
x = 20
Explanation:
The angles that are marked are called "vertical angles" (I think of a pair of scissors) The two angles are equal to each other. (They get bigger or smaller together, like a pair of scissors)
So, set them equal to each other and solve.
3x + 50 = 6x - 10
SUBTRACT 3x from both sides.
50 = 3x - 10
ADD 10 to both sides.
60 = 3x
DIVIDE both sides by 3.
20 = x