Final answer:
To complete the square in this equation, you should add 36 to both sides.
Step-by-step explanation:
To complete the square in the equation x^2 - 12x = 16, we need to add a number to both sides of the equation. The number that should be added is equal to half the coefficient of the x term squared. In this case, the coefficient of the x term is -12, so we add (12/2)^2 = 36 to both sides of the equation.