First, figure out how far Terrell plans to drive:
(50 mph)(2.75 hrs) = 137.5 miles
Next, using this distance and the fuel econ rating of 25 mpg, find the number of gallons required:
137.5 miles
------------------ = 5.5 gallons
25 mi/gal
Terrell will need 5.5 gallons of gas to make this 137.5 mile trip at 50 mph for 2.75 hours.