Answer: [tex]6+(7+8)=21[/tex]
Step-by-step explanation:
1. By definition, the associative property of addition is:
[tex](a+b)+c=a+(b+c)[/tex]
This property says that you can group the numbers in different ways and you will obtain the same result.
2. Therefore, if you have the following expression:
[tex](6+7)+8=21[/tex]
You apply the Asociative property of addition by regrouping the numbers as following:
[tex]6+(7+8)=21[/tex]
3. Then, you can conclude that the correct option is B.