Two angles are complementary if the sum of their angles equals 90^o.
If one angle is known, its complementary angle can be found by subtracting the measure of its angle from 90^o.

Example: What is the complementary angle of 43^o?
Solution: 90^o  -  43^o  =  47^o

Two angles are supplementary if the sum of their angles equals 180^o.
If one angle is known, its supplementary angle can be found by subtracting the measure of its angle from 180^o.

Example: What is the supplementary angle of 143^o?
Solution: 180^o  -  143^o  =  37^o