Write an integer that represents a $3 loss.

-3 or -$3.

Step-by-step explanation:

First, the set of integer numbers is the set of all the whole numbers (negatives, zero, and positives).

We want to write a $3 loss, now, the most important part here is that we have a loss, so we must represent this with a negative number.

Then we can write this as:

"An integer that represents a $3 loss"

is -3 or -$3 (if we want to also respect the units)