Answer:
x = 12
Step-by-step explanation:
For trapezoid DEFG to be isosceles, measures of it's base angles must be equal.
i.e.
[tex] m\angle E =m\angle F[/tex]
[tex] (5x+15)\degree =(7x - 9)\degree [/tex]
5x + 15 = 7x - 9
5x - 7x = - 15 - 9
-2x = - 24
2x = 24
[tex] x = \frac{24}{2} [/tex]
x = 12
