Well,
5 + (-2)
"Five plus the quantity negative two."
Adding a negative quantity is the same as subtracting the positive quantity.
For example: 0 + (-1) = 0 - 1 = -1
Another situation: 0 - (+1)
You have to realize that any number (say 5, for example) without a sign in front of it is automatically positive.
Technically, if we "show signs," we will get +0 - (+1)
We can really just omit ("hide signs") the positive signs.
0 - 1 = -1
Yet another situation: 0 - (-1)
Subtracting a negative can be re-worded as "subtracting from the negative." It sounds like it is taking away from the negative, bringing the integer closer to zero. Subtracting a negative is the same as adding a positive.
0 - (-1) = 0 + (+1) or 0 + 1 = 1
In your case: 5 + (-2):
5 + (-2) = 5 - 2 or 3 or +3