Answer: 14 miles ≤ D ≤ 22 miles.
Step-by-step explanation:
The mean distance traveled per gallon, is 18 miles.
But this can fluctuate, at most, by 4 miles.
Because we have here the "at most", we know that we should use the ≤, ≥ symbols.
Then, if the mean is 18mi, the range of possible distances traveled per gallon is:
(18 miles - 4 miles) ≤ D ≤ (18 miles + 4 miles)
Where D is the distance.
14 miles ≤ D ≤ 22 miles.
So the truck can get between 14 miles and 22 miles per gallon on the highway.
