Final answer:
An equation to represent the gas left in the car can be stated as y = 18 - 2.5x, where x is the number of hours into the trip and y is the amount of gasoline left.
Step-by-step explanation:
The equation to represent the amount of gas left in a car after each hour of a trip can be derived from understanding the initial amount of gasoline and the consumption rate per hour. We start with 18 liters of gas at the beginning of the trip, and 2.5 liters are used every hour. If we let x represent the number of hours traveled, and y represent the amount of gasoline left after x hours, we can write the equation as y = 18 - 2.5x.
This linear equation shows a direct relationship between the time traveled and the amount of gasoline used. The slope of the equation, -2.5, indicates the rate at which gas is being used every hour, while the y-intercept, 18, shows the original quantity of gas in the car. Thus, as time goes on (with each passing hour), the amount of gasoline decreases by 2.5 gallons.