The sum of the angles in a triangle is 180. Let x be one acute angle and y be the other. We know one is 5 times larger so let’s say 5x = y. Now,
x + y + 90 = 180
x + 5x + 90 = 180
6x + 90 = 180
6x = 90
x = 15
So y = 5x = 5(15) = 75
The two angles are 15 degrees and 75 degrees