Hi there!
I am not sure which "x" you are talking about, the one for the third angle or the one in the parentheses representing another angle.
If you are wondering what the value of "x" being the third angle is, the answer is 60° since this is an equilateral triangle and all the angles are equal to 60°.
But I am pretty sure that you are looking for the value of the "x" in the parentheses. To find its value, you need to create an equation and solve it by isolating "x". Since we know that all the angles are equal to 60°, your equation should look like this :
2x - 4 = 60
Add 4 on each side of the equation
2x = 64
Divide each side of the equation by 2
x = 32
There you go! I really hope this helped, if there's anything just let me know! :)