Study the following diagram of circle C, where AB¯¯¯¯¯¯¯¯ is a diameter that bisects the chord EF¯¯¯¯¯¯¯¯.
The circle as described in the problem. Segments C E and C F are marked congruent.


If m∠ACF=2(7x−4), what is the value of x?
Enter the correct value.