Answer
$$9x − (−4x)$$
or
$$13x$$
Work Step by Step
We need to translate the different parts of the statement in order to put together an expression.
"The difference between" means to subtract.
"9 times a number" means "9x."
"−4 times a number" means "−4x."
Now, we can put together the expression:
$$9x − (−4x)$$
Simplify:
$$9x + 4x$$
Add:
$$13x$$
