In triangle ABC, the external angle at vertex B is 40 degrees greater than the external angle at vertex A

In triangle ABC, the external angle at vertex B is 40 degrees greater than the external angle at vertex A, and angle C is 40 degrees. Determine which side – AB, BC or AC – is the largest.

Let the external angle at the vertex A be equal to x, then the external angle at the vertex B is equal to x + 40 degrees.
The sum of adjacent angles is 180 degrees, which means angle A = 180 degrees, angle B = 180 x-40 degrees.
The sum of the angles of the triangle is 180 degrees, so let’s make the equation:
angle A + angle B + angle C = 180;
180’s + 180’s-40 + 40 = 180;
2x = 180;
x = 180/2 = 90 degrees.
We get: angle A = 180-90 = 90 degrees, angle B = 180-90-40 = 50 degrees, angle C by condition is 40 degrees.
In a triangle opposite the larger angle there is a large side, which means that the side BC, which lies opposite the angle A, is the largest.