the family have 700$
they paid 500$ for the first two hours, so they still have 700 - 500 = 200$
if for every half hour 50$, and they have 200$, so you divide 200 by 50, which it's equal to 4
and since every 50$ give you half hour, which is equal to 30 minutes, so they will have 30 x 4 = 120 additional minutes
120 minutes = 2 hours
so the family can rent the boat for 2 + 2 = 4 hours
Hope this Helps :D
