How do i solve this? what do they mean

Complimentary angles add to equal 90°. Write two equations to solve for two variable.
J + K = 90
J = K - 18

use substitution or elimination to solve
I will use substitution. substitute (K - 18) for J in the first equation to combine equations into one in only variable K.

(K - 18) + K = 90
2K - 18 = 90
2K = 90 + 18
2K = 108
K = 108/2
K = 54°

J and K are complimentary.
J + 54° = 90°
J = 36°