Question

Finding the value of x
Examine triangle ABC.

Triangle A B C. Angle B is 79 degrees. Exterior angle to A is (x + 5) degrees and the exterior angle to C is x degrees.

What is the value of x?
37
48
127
138

Answer 1

Exterior angle at A = B + C, so x + 5 = 79 + C -> C = x - 74.
Exterior angle at C = A + B, so x = A + 79 -> A = x - 79.

Sum of interior angles: A + B + C = 180:
(x - 79) + 79 + (x - 74) = 180 -> 2x - 74 = 180 -> 2x = 254 -> x = 127.

Answer: 127.