Which promblem can be solved using 3 times 7=21

Jessica is a custodian at oracle arena.she waxes 20 m2 of the floor in 3/5 of an hour. jessica waxes the floor at a constant rate.at this rate how many sqaures meters can she wax per hour

Tcan be concluded that % of the seniors would prefer to see more candid pictures in this year's edition of the yearbook.

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