Question

What is the value of y ?

Answer 1

`\angle \: B = \angle \: C \: = 40° \\ \angle \: A + \angle \: B + \angle \: C = 180° \\ \angle \: A + 40° + 40° = 180° \\ \angle \: A = 100° \\ 2y + 20 = 100 \\ 2y = 80 \\ y = 40`

Answer 2

ABC is an isosceles triangle so <B = <C = 40

Sum of interior in a triangle = 180

<A = 180 - <B - <C

<A = 180 - 2(40)

<A = 180 - 80

<A = 100

Given: <A = 2y + 20

Plug in

2y + 20 = 100

2y = 80

y = 40

Answer

y = 40