Final answer:
To find what number added to negative seven equals nine, you add seven to both sides of the equation x + (-7) = 9, which simplifies to x = 16. So, the answer is 16.
Step-by-step explanation:
The question is asking to solve an equation where an unknown number when added to negative seven results in nine.
This is a basic algebraic problem involving positive + negative numbers.
To solve for the unknown number, we can use the rule for addition with numbers having opposite signs:
subtract the smaller number from the larger number, and give the result the sign of the larger number.
In this case, since we have the equation x + (-7) = 9, we want to isolate x by adding 7 to both sides of the equation.
This gives us x = 9 + 7, which simplifies to x = 16.
Therefore, the number that added to negative seven equals nine is 16.