Final answer:
To solve the equation 9 - ? = -4, we need to change the sign of the unknown and perform the operation, which leads us to the solution that the number replacing the question mark is 13.
Step-by-step explanation:
The equation 9 - ? = -4 is asking us to find the value that should replace the question mark so that the statement is true.
To solve this, we apply the rule for subtraction by changing the sign of the number we are subtracting and then follow the addition rules as follows:
- First, we change the equation to addition: 9 + (-?) = -4.
- To isolate the unknown, we move the 9 over to the other side by subtracting it from both sides: -? = -4 - 9.
- Now, we apply the rule that when two numbers with the same sign add together, you add the absolute values and keep the sign: -? = -4 - 9 = -13.
- The question mark is representing a negative number, so to find its positive equivalent, we change the sign: ? = 13.
Therefore, the number that should replace the question mark to make the equation true is 13.