If <x and <y are complementary angles and m<x =48 degrees , what is the measure of <y?

42
Complementary means the two angles are equal to 90°.
So, if ∠x + ∠y = 90°, then they are complementary.
∠x + ∠y = 90°
48 + y = 90
y = 90 - 48
y = 42