A right triangle has acute angles whose measures are in the ratio 1:3

Well..... they sum to 90 degrees

And...if they're in the ratio of 3 : 1, there must be 4 parts to this 90 degrees......so....each part is 90/4 = 22.5 degrees

So  3 x 22.5 = 67.5 degrees   and that's the larger angle

And the other is just 1 x 22.5  =  22.5  degrees