Answer:
C) 5
Step-by-step explanation:
The measure of angle TSU is 75°. (180° - 105° because it is a flat angle)
The sum of all the angles of a triangle is 180° as well.
You can write an equation to solve for x.
12x + 9x + 75 = 180
Isolate x.
12x + 9x = 180 - 75
12x + 9x = 105
Add the 12 and the 9.
21x = 105
Find what x is.
x = 105 ÷ 21
x = 5
