Respuesta :

Vertical Angles have equal measure, so set the expressions equal to each other, creating an equation, and solve for x:

mE = mF
9x + 12 = 3x + 24
- 3x          - 3x
------------------------------
6x + 12 = 24
     - 12      - 12
-------------------------
         6x = 12
         ---    ----
          6       6

           x = 2

Check this to be sure:  mE = 9(2) + 12 = 30 ;   mF = 3(2) + 24  = 30  YEP

vertical angles equal each other so you have

 angle E = angle F

9x+12 = 3x +24

subtract 12 from each side

9x = 3x +12

subtract 3x from each other

6x =12

divide both sides by 6

x = 12/6 = 2

 x = 2