Two rental car companies are running specials this month. At Kimi's Rentals, customers will pay $40 to rent a mid-sized car for the first day, plus $2 for each additional day. At Morristown Rent-a-Car, the price for a mid-sized car is $30 for the first day and $3 for every additional day beyond that. At some point, renting from either one of the companies would cost a customer the same amount. How many additional days would that take? ​