Final answer:
The algebraic expression to determine the number of seats in each car of a roller coaster with 4 cars and 21 passengers with 3 seats empty is solved by the equation 4x - 3 = 21, resulting in x = 6, which means there are 6 seats in each car.
Step-by-step explanation:
The question asks for the algebraic expression to determine the number of seats in each car of a roller coaster. The roller coaster has 4 cars, and there are 21 passengers with 3 seats empty. To find the number of seats in each car, we assume that all cars have the same number of seats and that all passengers are seated, filling up as many seats as possible.
To find the number of seats in each car, we can set up a proportion using the given information. We know that there are 4 cars, and 21 passengers with 3 seats empty. So, the total number of seats is 21 + 3 = 24. Since there are 4 cars, the number of seats in each car can be found by dividing the total number of seats by the number of cars: 24 / 4 = 6.
Let's denote the number of seats in each car as x. Since there are 4 cars, the total number of seats is 4x. Given that three seats are empty, the total number of seats filled by passengers will be 4x - 3. Since there are 21 passengers, we can write the equation 4x - 3 = 21.
To solve for x, we add 3 to both sides of the equation to get 4x = 24. Then, we divide by 4 to find x, which results in x = 6. Therefore, there are 6 seats in each car.