A teacher asked the class to solve the equation 3 (x+2) = 21. Robert wrote 3x + 6 = 21 as his first step. Which property did he use?

Distributive Property of Multiplication over Addition

Step-by-step explanation:

Robert multiplied the 3 by everything in the parenthesis, so

3*x=3x

and

3*2=6

This is called the Distributive Property. To be more specific, he is multiplying 3 by two the terms being added in the parenthesis, which is x+2.

This is called the Distributive Property of Multiplication over Addition.

Distributive Property