Let x be the number of days for the trip. With this representation and dropping the dollar sign, the Sand's Car Rental will charge a total of 50x + (0.1)(300) while Beach Car Rental will charge 60x. Equating the two charges, 50x + 30 = 60x. This gives an answer of x = 3. Therefore, the trip should take 3 days for the charges to be equal.