Question

The value of x is _____

Answer 1

Outside angle = addition of the two inner angles.

45x = 25x + 57 + x

45x = 26x + 57

45x - 26x = 57

19x = 57

x = 57/19

x = 3

Did you follow the logic?

Answer 2

We only need one simple theorem for this.

Theorem 7 - The Exterior Angle Theorem: An exterior angle of a triangle is equal to the sum of the two remote interior angles.

So in this case, the measurement of the exterior angle is (45x)°, and the interior angles are (25x)° and (57 + x)°.

=> Therefore, we have:

25x + (57 + x) = 45x

25x + x - 45x = - 57

-19x = -57

x = -57/(-19) = 3

So x = 3