Find the measure of the complement of angle kma.

We have a few steps to figure the complement of ∠KMA. We know what is given will equal a straight line so we  set the two expressions to equal 180.

(2x - 3) + (7x + 21) = 180
2x - 3 + 7x + 21 = 180          (combine like terms)
9x + 18 = 180                        (subtract 18 from both sides)
9x = 162                              (divide both sides by 9)
x = 18                          (use this to find the value of ∠KMA)

2x - 3
2(18) - 3
36 - 3
33                  ∠KMA is 33°

to find the complement, we subtract the 33 from 90 and we get the complement to ∠KMA is 57°