Answer: - 6.
Step-by-step explanation:
The set of integers is the set of the whole numbers. {..., -1, 0, 1, 2, ...}
We want to represent a loss by 6 yards in football.
Because this is a loss, we should use a negative number, then we can use:
-6
This represents the number of yards by which your team losts.
Notice that I did not write the units, this is because:
-6 yards is a measure, furthermore can be "an integer number of yards"
-6 is an integer.