Commutative Property of Addition
Commutative property of addition:
$$$\color{purple}{a+b=b+a}$$$
What does it mean?
It means, that order of numbers doesn't matter.
Indeed, suppose your first friend (let's call it Tom) gave you 3 apples, then your another friend (let's call it Jim) gave your 4 apples. You got total of 7 apples.
But does really matter, who gave the apples first? If Jim gave you 4 apples and then Tom gave you 3 apples, you got also 7 apples.
Warning: it doesn't work with subtraction, i.e. $$${a}-{b}\ne{b}-{a}$$$.
For example, $$${4}-{3}\ne{3}-{4}$$$.
However, commutative property of addition works for negative numbers (in fact, for real numbers) as well.
Example 1. $$${3}+{\left(-{4}\right)}={\left(-{4}\right)}+{3}$$$.
Example 2. $$${\left(-{2.51}\right)}+{\left(-{3.4}\right)}={\left(-{3.4}\right)}+{\left(-{2.51}\right)}$$$.
Example 3. $$$\frac{{5}}{{8}}-\frac{{2}}{{3}}=\frac{{5}}{{8}}+{\left(-\frac{{2}}{{3}}\right)}={\left(-\frac{{2}}{{3}}\right)}+\frac{{5}}{{8}}$$$.
Conclusion. So, the basic rule here is following: whenever you see addition, you can interchange addends.