Answer:
A 70
Step-by-step explanation:
We know that angle B and angle C are equal because this is an isosceles triangle and the angles at the base of the equal sides are equal.
The three angles of a triangle add to 180 degrees
A + B+ C = 180
40 + C + C = 180 since B = C
Combine like terms
40 + 2C = 180
Subtract 40 from each side
40-40 + 2C = 180-40
2C = 140
Divide by 2
2C /2 =140/2
C = 70
