When adding or substracting with negatives(-), keep these things in mind:

(+) + (+) = (+)                    

(-) + (-) = (-)

(+) + (-) = ( take the sign of the LARGEST NUMBER and substract)

EX:  8 + (-3) = 5

 (+) - (-) = [ double minus becomes a (+)]

EX: 10 - (-5) = 5