Answer:
a. Linear pair theorem
b. x = 40
Step-by-step explanation:
a. x° and (4x - 20)° are angles on a straight line, so, they are a linear pair. Therefore, we would apply the linear pair theorem, which says the sum of a linear pair gives us 180°.
b. x° + (4x - 20)° = 180° (linear pair theorem)
Solve for x
x + 4x - 20 = 180
5x - 20 + 20 = 180 + 20
5x = 200
5x/5 = 200/5
x = 40
