the function f (x) = 150+35x represents the amount of money a hotel charges (in dollars) for x nights including a $150 charge for parking

For the 4 night at the hotel, the answer is 290 since you insert 4 in where the x should be 150+35 (4). For the second question, the answer is 8 since you subtract the money you have (430) by the parking cost (150). This lead to 280 and you divide it by the amount you need to spent on hotel charge per night (35) and you get 8. That means that you can spend 8 night at the hotel.