Question

In triangle ABC, angle A = (4x+5) and angle B = (5x-1)

Answer 1

It is an isosceles triangle, therefore

$m\angle A=m\angle B$

$4x+5=5x-1\ \ \ |-5\\4x=5x-6\ \ \ |-5x\\-x=-6\to x=6$

$m\angle A=m\angle B=4\cdot6+5=24+5=29^o$

We know:

$m\angle A+m\angle B+m\angle C=180^o$

therefore

$29^o+29^o+m\angle C=180^o\\\\58^o+m\angle C=180^o\ \ \ |-58^o\\\\m\angle C=122^o$