Answer: Your equation is y=85(1.18)^x and it will take a little under 12 years for the population to reach 600.
Explanation:
The equation for an exponential equation is y=ab^x
Change 18% to a decimal and than add 1 to it because it has to be above 1 to increase.
This is your equation ---> y=85(1.18)^x
After 11 years, the population of the frogs would be 525 and for 12 years, the population will be 619. So for the population to reach 600, it will take a little under 12 years.