Use x to represent the first two angles. If the third angle is 3 times as large as the first, it can be represented as 3x. So, your angles are x, x, and 3x. These need to all add to 180 degrees, since it’s a triangle.
x + x + 3x = 180 —> Simplify the left side. 5x = 180 —> Divide by 5. x = 36
So the first two angles are 36 degrees, and the third angle is 3 times that, which is 108 degrees.
