Answer:
Explanation:
The missing options are:
For this exercise it is important to remember the mulitplication of signs:
By definition, the sum is the result of an addition.
Therefore, you need to add the numbers given in the exercise (-15 and 6) in order to find its sum. This is:
(Since the greatest number has a negative sign, the sum is negative).
Knowing this, you can check each option to find the expression whose sum is -9:
The answer is the option "d".