Question

TOXIC CLEANUP
Three months after cleanup began at the dump site, 800 cubic yards of toxic waste had yet to be removed. Two months later, that number had been lowered to 720 cubic yards.

a. Write an equation that mathematically describes the linear relationship between the length of time x (months) the cleanup crew has been working and the number of cubic yards y of toxic waste remaining.

b. Use your answer to part a to predict the number of cubic yards of waste still be on site 1 year after the cleanup project began.

Answer 1

Treat the question as if you had two ordered pairs
(3,800) and (5,720)

slope = (720-800)/(5-3) = - 40

using(3,800)
y - 800 = -40(x-3)
y = -40x + 920

b) so after 1 year, x = 12
y = -40(12) + 920 = 440

state your conclusion using the proper units