Question

Phan fills the tank of her car with gasoline before starting her road trip. The table below shows the amount of gas left in her tank as she drives.

Number of Hours vs. Amount Left in Tank
Number of Hours Spent Driving (h)

3

5

7

9
Amount of Gas Left in Tank, in gallons (g)

12

8

4

0

Which equation models the amount of gas left in the car as Phan drives, and how many gallons of gasoline does it take to fill her tank?
g = 18 – 2h; 18 gallons
g = 18 – 2h; 16 gallons
g = 3h + 3; 30 gallons
g = 3h + 3; 12 gallons

Answer 1

Compute the slope: between h = 3 and h = 5, g drops from 12 to 8, so slope = (8−12)/(5−3) = −4/2 = −2.
Use a point to find intercept: 12 = −2(3) + b → b = 18.
So g = 18 − 2h, and the tank holds 18 gallons.