Respuesta :

mathecoach

A + B + C = 180

A = B --> B = A

A = 4·C --> C = 1/4*A

A + A + 1/4*A = 180

2.25*A = 180

A = 80

choixongdong

#4

In triangle ABC, AB = BC. it's isosceles triangle so <A = <B

Lets x = measure of angle C, so <C = x

<A is 4 times <C so <A = 4x but <A = <B so <A = <B = 4x

Sum of interior angles in a triangle = 180

x + 4x + 4x = 180

9x = 180

x = 20

<A = 4(20) = 80°

Answer is (3) . 80°