I’m pretty sure you meant x^2 so I’m going to answer based off that. Change the equation to look like this:
x^2-8x+12=0
Then you factor it. So it would turn into:
(x-6) (x-2) = 0
To solve for zeros, you just put the opposite of the number. In this case, since we have (x-6) the zero here would be positive 6 and for the (x-2), the zero would be positive 2. This is because if you put x-6 = 0 and solved for x, you would add 6 to each side making it a positive 6. The same applies for the (x-2).