Answer :

iGreen
Complementary angles add up to 90 degrees.

So we can write:

42 + x = 90

To solve, subtract 42 to both sides:

x = 48

So the complement of a 42 degree angle is a 48 degree angle.
Complementary angles measures to the sum of 90 degrees. Since there is already an angle of 42 degrees, simply subtract 90 from 42, and you get 48 degrees...

angle A + angle B= 90 degrees, so

42 +x=90
x=48