6. A surf board rental company charges $25 for the first hour and $10 for each additional hour. Which equation could be solved to find the number, x, of additional hours rented if the total cost of the rental was $75? a)25x + 10 = 75 b)25 + 10x = 75 2)75 - 25x = 10 d)25 - 10x = 75