Find the value of x triangles help pls :(

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?

The radius of the earth is two times the radius of the moon. what fraction of the volume of the earth is the volume of the moon?

Find the domain and range of the following function f(x) = 51x - 21+ 4