I need help ASAP can you guys please help me

Idon’t understand this.. will someone ? will mark brainliest along with 20 points.

Find the greatest common factor of the followig monomials 21u^5v,3u^4v^6, and 3u^2v^5

Part a: sam rented a boat at $225 for 2 days. if he rents the same boat for 5 days, he has to pay a total rent of $480. write an equation in the standard form to represent the total rent (y) that sam has to pay for renting the boat for x days. (4 points)