Answer:
a = 85
Explanation:
the exterior angle of a triangle is equal to the sum of the 2 opposite interior angles.
5x is an exterior angle of the triangle , then
5x = 2x + 57 ( subtract 2x from both sides )
3x = 57 ( divide both sides by 3 )
x = 19
Then
5x = 5 × 19 = 95
5x and a lie on a straight line and are a linear pair which sum to 180° , so
5x + a = 180 , that is
95 + a = 180 ( subtract 95 from both sides )
a = 85