What number can be added to 9 to get result of 0

The answer is - 9. because - 9+9=0

To solve this problem, we should set up an equation, letting x be the unknown number.

9 + x = 0

Next, we should subtract 9 from both sides to cancel out the + 9 on the left side of the equation and get the variable alone.

x = - 9.

Therefore, the number you are looking for is - 9.