There are basically four combinations that you may have to deal with in signed computations:
1) positive + positive 2) positive + negative 3) negative + positive 4) negative + negative
Situation One: Positive Plus Positive
Your answer must be positive when adding two positive numbers.
EXAMPLES: 1 + 1 = 2 100 + 200 = 300 33 + 22 = 55
EXAMPLES: -1 + -1 = -2 -100 + -200 = -300 -33 + -22 = -55