Find the missing part (labeled ?)

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 volume of a rectangular prism if the length is 10.4 mm the width is 5 mm in the height is 8 mm

You have 6 dollars +12 pennies +to quarters + 4 dimes=2 nickels how much do you have