Answer: x = 12
=====================================================
Work Shown:
I'm assuming the diagram shows that interior angles F and G are 24 and 12+5x respectively.
We can use the remote interior angle theorem to get:
(interior angle F)+(interior angle G) = exterior angle FEH
(24) + (12+5x) = 8x
5x+36 = 8x
36 = 8x-5x
36 = 3x
3x = 36
x = 36/3
x = 12