On the first day, they traveled for 10 hours with an average speed of 60 mph. Which means on the first day they traveled 600 miles.
Since the total distance is 1023 miles and presumably they will be going at a speed of 60 mph. We divide the miles by the rate:
1023/60 = 17.05
So it will take 17.05 hours to drive the whole way to Florida.