Assuming that there is a "plus" after the second 58, the answer is - the associative property of addition.
I assume you mean: (54 + 23) + 87 = 45 + (23 + 87). That's an example of the associative property of addition.
The Associative Property of addition
23 plus 7684235 equals 7684258.
It equals 435
8 plus 15 = 23
-23
Who is the idiot that told you that - everyone knows that 23 plus 60 equals 83 !
22
74 + 23 = 97
It is: 157+23 = 180
29 + 23 = 52
23 + 4 = 27
21
123