Hey there.
The answer for this question is Associative Property of Addition; let's evaluate.
In the photo above, we have an equation with the same numbers, but placed in different areas of each side.
Let's apply this property to a different example;
(a + b) + c = a + (b + c); let's input some values for our variables.
a = 1, b = 2, and c= 3.
(1 + 2) + 3 = 1 + (2 + 3)
3 + 3 = 1 + 5
6 = 6
This property is true.
I hope this helps!