If x = 30, what is the estimated amount of diesel remaining?

• A. 16 gallons
• B. 10 gallons
• C. 20 gallons
• D. 24 gallons

Answer: (A)

Reading a linear relationship from a graph or line lets you estimate the value of a quantity at a specific x. Here, diesel remaining changes at a steady rate as x changes, so to find the amount when x is 30 you locate x = 30 on the horizontal axis and read the corresponding y-value on the line. The read value is about 16 gallons, so that is the estimated amount remaining.

If you wanted to check quickly with a simple idea: since the line shows a constant rate of decrease, the change over 30 units of x results in a fixed drop in remaining diesel, and reading the line at x = 30 gives the remaining amount as 16 gallons.