Answer:
a. 20
Step-by-step explanation:
You are solving vertical angles. Put the measurements equal to each other:
x + 40 = 3x
Isolate the variable, x. Note the equal sign, what you do to one side, you do to the other. Subtract x from both sides.
x (-x) + 40 = 3x (-x)
40 = 3x - x
40 = 2x
Isolate the variable x. Divide 2 from both sides:
(2x)/2 = (40)/2
x = 40/2
x = 20
a. 20 is your answer.
~
