Explanation:
Let,
Angle 1 = x
Angle 2 = x/3
Angle 3 = 120
We know that
Sum of all angles in a triangle = 180
x + x/3 + 120 = 180
3x + x + 360/3 = 180
4x + 360 = 180 × 3
4x = 540 - 360
4x = 180
x = 180/4
x = 45
Now,
Angles are
x = 45⁰
x/3 = 45/3 = 15⁰