Answer: Associative property of addition.
Explanation:
The rule for the Associative property of addition is:
![a + (b + c) = (a + b) + c](https://img.qammunity.org/2020/formulas/mathematics/high-school/9ug35hizs3d6zgoy8t5t4409bizucpf2qi.png)
Therefore, this property establishes that it does not matter how you group the numbers, the sum will not change.
You can observe that, in this case, the numbers of the given addition can be grouped as
or
, and the sum will be the same.
Then, you get:
![6 + (14 + 70) = (6 + 14) + 70 = 20 + 70 = 90](https://img.qammunity.org/2020/formulas/mathematics/middle-school/a71liot634v6zeuaapde4ljjd3desjocqx.png)