Final answer:
The property justifying k = 8 when k - 8 = 0 is the Addition Property of Equality, which maintains the balance of the equation when the same number is added to both sides.
Step-by-step explanation:
If k - 8 = 0, the property that justifies k = 8 is the Addition Property of Equality. This property states that if you add the same number to both sides of an equation, the balance of the equation remains unchanged. In this case, you would add 8 to both sides of the original equation (k - 8 + 8 = 0 + 8) to isolate k on one side, giving k = 8 as the result.