Question

9 + (–11) + (–10

Answer 1

9 + (-11) + (-10)
9 - 11 - 10
9 - 21
- 12 <-- your answer

Answer 2

Quick lesson...
when you multiply a positive and a positive, answer is positive
when you multiply a negative and a negative, the answer is positive
when you multiply a negative and a positive, answer is negative.

In other words, if your multiplying and the signs are the same, it will be positive. If the signs are different, it will be negative.