We are given one angle is 3 times less than other.
Let us assume one angle measure is x degrees and another is 4x.
Because x is 3x less than 4x. ( We can check 4x-x= 3x)
Sum of complementary angles is 90 degrees.
So, we can setup an equation
First angle measure + first angle = 90 degrees.
x+4x = 90.
Adding x and 4x, we get 5x.
So, 5x = 90.
Dividing both sides by 5, we get
5x/5 = 90.
x= 18.
So, one angle is of 18 degrees.
Another angle = 4x = 4 times 18 = 72 degrees.
So, required angles are of 18 degree and 72 degree.