Question

Δ ABC is isosceles. Angles B and C are congruent.

If m∠B = (5x + 5)° and m∠C = (7x - 25)°, Find m∠A.

Answer 1

what you know about isoscele triangles ?
has two angles and the corresponding sides congruent - how is given

- in case of your posted problem angle B congruent angle C
given m<B = (5x+5)°
and m<C=(7x-25)°

in this way we can write

5x+5 = 7x -25

using this equation you can calcule the x value
- then you substitute the x value inside these expressions of m<B and m<C in place of x you can calcule easy the value of angle measure of B and C
ATTENTION ! NEED BE EQUAL BC. ARE CONGRUENT ANGLES !!!

- hope you know that the sum of angles measure of a triangle is equal 180 degrees

- so assuming angle measure of B and C and this sum then subtract from 180 you will get easy the angle measure of A

hope helped understandably easy

@supie

Answer 2

@AZ any idea here pls. ? ty