Answer: Hong drove the truck for 294 miles.
Explanation:
Let m represent the number of miles for which he drove the truck.
There was a base fee of $20.95, and there was an additional charge of 90 cents for each mile driven. It means that the expression for the cost of driving the truck for m miles in a day is
20.95 + 0.9m
Hong had to pay $285.55 when he returned the truck. It means that
20.95 + 0.9m = 285.55
0.9m = 285.55 - 20.95
0.9m = 264.6
m = 264.6/0.9
m = 294 miles