Question

What is the value of x?

Answer 1

Answer: Choice D) 30

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How I got this answer:

Use the exterior angle theorem. This theorem says adding any two remote interior angles of a triangle is the sum equal to the exterior angle.

The interior angles x and 70 add to x+70, which is equal to the exterior angle 100

x+70 = 100

x+70-70 = 100-70

x = 30

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Another route is to mark y as the angle adjacent to 100, and this angle y is inside the triangle. It is the third missing angle. Solve 100+y = 180 for y to get y = 80

The triangle has interior angles 80, 70 and x. They add to 180 leading to

80+70+x = 180

x+150 = 180

x+150-150 = 180-150

x = 30

Answer 2

Answer:

30 degrees

Step-by-step explanation:

first find the angle of the other angle that is not found

180-100=80 degrees

since all angles of triangle add up to 180 degrees..

180-80-70= 30 degrees