Answer:240 miles
Step-by-step explanation: the reason they have 240 miles left to drive is because on the first day they drove 365 miles so you would subtract that by the total and you get 971 miles then you subtract 421 miles witch is what they drove on the second day by 971 and you get 550 and then you subtract 550 by 310 miles witch is what they drove on day 3 and then you get 240 miles.