Answer:
x = 3
Explanation:
The exterior angle of a triangle is equal to the sum of the 2 opposite interior angles.
∠QRT is an exterior angle of the triangle
∠RTS and ∠RST are the 2 opposite interior angles, thus
45x = 25x + 57 + x
45x = 26x + 57 ( subtract 26x from both sides )
19x = 57 ( divide both sides by 19 )
x = 3