In the figure, (AC) ̅≅(AB). Find the value of y in terms of x. If the vertex angle of an isosceles triangle is y and the exterior angle ABE is 3x+20.

Question

Answer: y= 6x-140

Pls explain it to me how they get the answer.

Answer 1

ABE+ABC = 180, so ABC = 180-ABE
ABC = (180-y)/2

so,

180-(3x+20) = (180-y)/2
160-3x = 90 - y/2
70-3x = -y/2
y = 6x-140