x - 4 = 4 - x
4 is subtracting on the left, then it will add on the right
x is subtracting on the right, then it will add on the left.
x + x = 4 + 4
2x = 8
2 is multiplying on the left, then it will divide on the right
x = 8/2
x = 4
So, there is only one solution