Since this line is one single line you want to add the two parts rather than multiply.
(x - 7) + (x - 3) = 12
x - 7 + x - 3 = 12
Next you want to simplify everything so add the values with the variables together and add the constants together
2x - 10 = 12
Get the term with the variable on one side
2x = 22
Divide by 2 on both sides to find x
x = 11