With vertical angles like this, since you know one side is 65 degrees, the opposite side is also 65 degrees.
65*2 = 130 degrees. 360-130=230 degrees. 230/2 = 115
z = 115 degrees
Equation time
(14x - 5) = 65
Add 5 to both sides
14x = 70
Divide each side by 14
x=5
z=115