It follows The Commutative Property of Addition.
Let us take a simple example of commutative property
What's the answer to this?
2+3
Yeah, that's an easy one!
2+3=5
How about switching the order... What do we get then?
3+2
Same thing, huh?
3+2=5
Well, if both things equal 5...
2+3=5=3+2
Then those things have to equal each other!
2+3=3+2