Answer:
t = 6.29 years
Explanation:
The general formula of an exponential function is
, where a is the initial value (i.e., value of y when x = 0), b is the base, and x is the exponent.
We can express rabbit population as a function of time in years, which means in our formula, r is like y and t is like x:

Because at time t = 0, the rabbit population is 20, we know that our a value for the equation is 20.
We can find b by simply plugging in 20 for a and any point for r and t like (1, 60):

Thus, the equation we will need to use to find the rabbit population is

It's helpful to use an inequality where the equation is greater than r since we want to know how many years it will take for the population to exceed 20000:

We can check our answer by plugging in 6.29 for t and check whether the answer we get is greater than 20000:
