The measure of angle X is 18 more than three times the measure of its complement. Find the measure of angle X.

The complement of an angle is 90 minus the angle, or

90 - x = complement angle

if x is 18 more than 3 times it's complement, then

x = 3 (complement angle) + 18

We can substitute "90 - x" for the "complement angle" in the second equation:

x = 3 (90 - x) + 18

distribute the 3 to the 90 and the x

x = 270 - 3x + 18

add 3x to both sides

4x = 270 - 18

4x = 252

x = 63

the measure of angle x is 63 degrees