STEP 1:
find the difference between the total miles of the trip (762 miles) and the miles already traveled (510 miles)
= 762 - 510
= 252 miles left of trip
STEP 2:
divide miles left from step 1 by 3 days
= 252 ÷ 3 days
= 84 miles per day
ANSWER: She needs to travel 84 miles each of the 3 days to complete the trip.
Hope this helps! :)