Does anyone know this?

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?

You can find the constant of proportionality by finding the ratio of

If olu is twice as old as funmi if the sum of their ages is 60 how old is olu