In the following example of "Simplifying an Expression", what reason would be used for step C?

Simplify the expression 3k + 7 + 2k and justify each step

3k + 7 + 2k = 3k + 2k + 7 A
= open parentheses 3k + 2k close parentheses + 7 B
= open parentheses 3 + 2 close parentheses times k + 7 C
= 5k + 7 D
A. Addition
B. Commutative Property
C. Associative Property
D. Distributive Property

Question

In the following example of "Simplifying an Expression", what reason would be used for step C?

Simplify the expression 3k + 7 + 2k and justify each step

3k + 7 + 2k = 3k + 2k + 7         A
                    = open parentheses 3k + 2k close parentheses + 7      B
                    = open parentheses 3 + 2 close parentheses times k + 7        C
                    = 5k + 7                 D
	A.	Addition
	B.	Commutative Property
	C.	Associative Property
	D.	Distributive Property