Question

For this figure, what is the value of x?

Answer 1

The sum of the interior angles of this triangle must be 180 degrees.

Adding them up: [28] + [58 + 77] + [x] = 180

Solving for x: 28+ 135 + x = 180

x = 180 - (28+35) = 117 (degrees) (answer)

Answer 2

The angles inside a triangle always add up to 180 degrees.
The whole thing is one big triangle made of two smaller ones.

28 + 58 + 77 + x = 180
163 + x = 180
x = 180 - 163
x = 17