Answer:
∠ C = 100°
Explanation:
since 2 sides of the triangle are congruent then the triangle is isosceles with base angles congruent.
consider the angle inside the triangle to the left of 140°
this angle and 140° are a linear pair and sum to 180°
angle + 140° = 180° ( subtract 140° from both sides )
angle = 40°
then the angle on the left of the triangle = 40° ( base angles congruent )
the sum of the angles in a triangle = 180° , so
∠ C + 40° + 40° = 180°
∠ C + 80° = 180° ( subtract 80° from both sides )
∠ C = 100°