The given triangle is an isosceles triangle because two sides are equal. This means that the base angles are equal.This means that the other base angle is also 70 degrees
Recall, the sum of the angles in a triangle is 180 degrees. This means that
x + 70 + 70 = 180
x + 140 = 180
x = 180 - 140
x = 40
Option A is correct