Answer
90$^{\circ}$ - x$^{\circ}$
Work Step by Step
The sum of two angles a$^{\circ}$ and b$^{\circ}$ is a$^{\circ}$+b$^{\circ}$ =90$^{\circ}$. therefor they are called complimentary angles.
The compliment of angle a$^{\circ}$is b$^{\circ}$ which can be written as b$^{\circ}$ = 90$^{\circ}$ - a$^{\circ}$
Hence compliment of x$^{\circ}$ is 90$^{\circ}$ - x$^{\circ}$
