Numbers Can be Positive or Negative:
Negative Numbers (−) Positive Numbers (+)
(This is the Number Line, read about Using The Number Line)

"−" is the negative sign. "+" is the positive sign
No Sign Means Positive

If a number has no sign it usually means that it is a positive number.

Example: 5 is really +5
Adding Positive Numbers

Adding positive numbers is just simple addition.
Example: 2 + 3 = 5

is really saying

"Positive 2 plus Positive 3 equals Positive 5"

You could write it as (+2) + (+3) = (+5)
Subtracting Positive Numbers

Subtracting positive numbers is just simple subtraction.
Example: 6 − 3 = 3

is really saying

"Positive 6 minus Positive 3 equals Positive 3"

You could write it as (+6) − (+3) = (+3)