The midpoint of chord AB is ( , ), and the slope of chord AB is

Imagine a new pasture with grass growing on it. every day after the seeds have germinated, the number of blades of grass in the pasture triples. after 18 days, the entire pasture is completely covered in grass. how many days did it take for the pasture to be one-third covered in grass?

What is the value of x? enter your answer in the box. (cm)

Which equation matches the graph shown ?