when youre adding negative numbers, you add them and put a negative sign (ex: -6 + -5=-11)
when you add negative and positive numbers(ex: -9 + 7) you subtract the numbers and take the sign of the bigger number (9-7=2, so the answer is -2 because the bigger number, 9, is negative
when you subtract 2 negative numbers you add them together and put a negative sign
when you subtract a neg. number and a pos. number (ex: -8 - 3) you add the numbers but the 3 becomes negative so the problem becomes -8 + -3. the answer is -11