-8/5+2/-5 is the same as -8/5 - 2/5, because the minus sign applies to the whole fraction not to just the top or just the bottom part. The fractions have the same denominator so we can write (-8-2)/5, that is we can add together the two negatives. How do you add two negative numbers? Think of the sign as indicating direction. Plus means go to the right or forwards and minus means go to the left or backwards. In this case take eight steps backwards then go back another two steps. How many steps backwards have you gone? 10, of course, which is -10. -10/5, if there was no minus, would be 2, so you do the division first then call the result negative, so the answer is -2. The rule is: if you multiply or divide two numbers with different signs (no sign at all means plus) the result is always negative; if the signs are the same, two positives or two negatives, the result is always positive.