find complement and supplement of x

Complementary angles add to 90

and

Supplementary angles add to 180.                  (just like Chris said)

If you can remember the 2 words it is easy to know which is which because 

2 C's make an S     (one reflected and sitting on top of the other one)          and 2*90=180

The complement of x = (90- x)

The supplement of x = (180 - x)