Question

450 square feet of the field were covered with weeds. Each year, Gloria removes 35% of the weeds. Which equation can be used to model the area covered with weeds, t, in square feet, as a function of the number of years, y, Gloria has owned the field?

Answer 1

This is an example of exponential decay.

F = P(1 + r)^t

F = future value
P = present value
r = yearly rate as a decimal (for decay, r is negative)
t = time in years

F = 450(1 - 0.35)^t

In your case, just change the variables.

t = 459(1 - 0.35)^y