Please explain this to me

Including 6% sales tax, an inn charges $135.68 per night. find the inns nightly cost

Liz is shipping a package to her friend. the maximum weight of a medium flat-rate box is 20 pounds, including the box which weighs 6 ounces. write and solve an inequality to describe the possible weight in pounds, w, of the contents that liz will ship to her friend if she must use a medium flat-rate box. use the drop-down menus to explain your answer.

What is the geometric mean of 3 and 7? a) square root of 21 b) 2 square root of 6 c) 2 square root of 7 d) 21