Final answer:
Subtracting a negative number is the same as adding a positive one. Therefore, -40 - (-30) + 10 - (-9) simplifies to 9.
Step-by-step explanation:
To solve -40 - (-30) + 10 - (-9), you need to understand how to deal with negatives. When you subtract a negative number, it's the same as adding a positive number. So -40 - (-30) becomes -40 + 30. Now the equation is -40 + 30 + 10 - (-9).
Combining the numbers, we have -10 + 10 + 9, which simplifies to 0 + 9, or 9.
Learn more about Subtracting Negatives