1. the complement is when two angles add up to 99 degrees and the supplement is when the two angles add up to 180 degrees.
2. Let x be the measure of the unknown angle .
3. Let 90 -x be it's complement and 180- x be the supplement of the angle .
4. Given 90-x=3x+9 the measure of the complement of an angle is 3x+9. Solve using the following steps.
99-x=3x+9
Add x-9 to both sides to isolate x-terms on right side and numbers on left
90-x+x-9=3x+9+x-9
90-x+x-9=3x+9+x-9
91=4x
divide by 4 to both sides yields
91/4=x
5. Given 3x+99=180-x. The measure of the supplement of an angle is 3x+99. So
3x+99=180-x
Add x+99 to both sides of equations to isolate x on right side and number on left
3x+99+x-99=180-x+x-99
4x=91
X=91/4
6. The angle is x=91/4
