"A.Write an equation that gives the number of cans recycled per pound of aluminum recycled as a function of the number of years since 1972."
You can obtain an equation of this straight or almost straight line using the two data points (5, 23.5) and (8, 33.1). "5" represents 1977, 5 years after 1972.
The slope of the line thru these 2 pts is
33.1-23.5 9.6
m = ---------------- = ------- = 3.2
8-5 3
Then the equation of the line is y-23.5 = (3.2)(x-5).