Respuesta :

altavistard
I don't see that you need to use that property here.  Simply multiply 3 by 7, obtaining 21, and be done with it.

7(3+x) is different and would require the Distributive Property of Mult.:

21 + 7x                 (Multiply each term inside parentheses by 7.)
kskora
Commutative property is (Order doesn’t matter.)
7x3=21. Is the same as 3x7=21