Question

30 points

What is the value of y?

Enter your answer in the box.


y =

Answer 1

Explanation:

Because of the Isosceles Triangle Theorem, angle B and angle C have the same measure. If angle B is 75, then so is angle C. By the Triangle Angle-Sum Theorem, all the angles of a triangle have to add up to equal 180 degrees. That means that angle A = 180 - 75 - 75 which is 30 degrees. Therefore,

Angle A = 30 degrees. By the substitution property of equality,

4y + 10 = 30 and

4y = 20 so

y = 5