x = one angle
y = other angle
y = 15+x
complements add to 90 degrees
x+y = 90
substitute for y (15+x)
x + 15+x = 90
combine like terms
2x+ 15 = 90
subtract 15 from each side
2x = 75
divide each side by 2
x = 75/2
x = 37.5
y = x+15
y = 37.5 + 15
y =52.5
The two angles are 37.5 and 52.5