"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). Â "5" represents 1977, 5 years after 1972.
The slope of the line thru these 2 pts isÂ
    Â
     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).