Response:

Step-by-step breakdown:
Kevin has already gathered five and a half gallons of water for his trip
He understands that he requires a minimum of 20 gallons of water for the journey.
The water is packaged in 32-fluid ounce (quarter-gallon) containers.
1 fluid ounce equals 0.0078125 gallons
32-fluid ounce 
Let x represent the number of 32-fluid ounce (quarter-gallon) containers needed to collect at least 20 gallons of water for the trip.
One container holds 0.25 gallons of water
Therefore, x containers hold 0.25x gallons of water
Thus, Kevin's total gallons of water =
Since it is given that he needs at least 20 gallons of water for the trip.
Hence, 
Thus, the algebraic inequality representing this scenario is 