The math is below, and the graph is attached.
Work Step by Step
We plug in the given values of x into the equation to find: A) $f(50) = 12 + .2(50) = 22$ B) $ f(100) = 12 + .2(100) = 32$ C) The graph is attached. D) In order to estimate, first draw a vertical line at t=80. Then, estimate the value of f(x) at the intersection. This value is 28 gallons. After all: $f(80) = 12 + .2(80) = 28$