Suppose that the weight (in pounds) of an airplane is a linear function of the total amount of fuel

Question

Suppose that the weight (in pounds) of an airplane is a linear function of the total (in gallons) in its tank. When graphed, the function gives a line with a slope of 5.6

With 52 gallons of fuel in its tank, the airplane has a weight of 2291.2 pounds. What is the weight of the plane with 87 gallons of fuel in its tank?

Answer 1

The line has the form y=mx+b, where y is the weight of the plane with gas in it, x is the amount of gas, and b is the weight of the plane when the gas tank is empty.
*From the information given: adding 35 gallons of gas adds 5.6*35=196 lb weight, so the plane weighs 2291.2+196 = 2487.2 lb.

By the way, had the question asked what b is, here's how to get it:
2291.2 = 5.6*57 + b
= 319.2 + b
b = 2291.2-319.2=1972 lb