Define variable for traveling 2345 total but I've already went 775 miles. If i want to split the remaining miles left into 5 days

X = (2345-775) / 5

Use x as the variable for the number of miles traveled in 1 day. The number of miles left to travel is equal to the total distance minus the distance already traveled:

(2345-775)

Then divide by the number of days, 5:

(2345-775) / 5