Every triangle always consists of three angles which altogether give 180⁰. Let's say that:
Angle 1 = x
Angle 2 = 3x
Angle 3 = x + 40
180 = x + 3x + x + 40
180 = 5x + 40 / - 40 (both sides)
140 = 5x / : 5 (both sides)
x = 28
Angle 1 = 28
Angle 2 = 3 * 28 = 84
Angle 3 = 28 + 40 = 68
Let's check if it gives us 180⁰:
28 + 84 + 68 = 180
So it's correct :)