What is the value of x of this triangle and angles

Answer:
x = 9
Step-by-step explanation:
The big triangle is twice as big as the little triangle bc of the info given on midpoints.
So AC is twice as big as DE.
3x - 15 = 2(6)
3x - 15 = 12 ADD 15
3x = 27 DIVIDE BY 3
x = 9