How do the rules for multiplying integers compare to those of multiplying rational numbers?

What is the equation of the linear function represented by the table?

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?

Translate the word phrase into a math expression. 15 fewer than the product of 4 and a number. (pls immediately)