Why is 0 considered a number when it is basically nothing?

The bike store marks up the wholesale cost of all the bikes they sell by 30% and andre wants to buy a bike that has a price tag of 125 what was the wholesale cost of the bike

Jeffery conducted a survey in his school and found that 30 of the 50 eighth grade students' favorite subject is mathematics. based on the results, jeffery concluded that out of the 200 students in his school, 120 students' favorite subject is mathematics. select the statement that is true about jeffery's conclusion. a. jeffery's conclusion is not valid because the sample was biased since only 200 students were surveyed. b. jeffery's conclusion is valid because the sample was random since all of the students were eighth grade students. c. jeffery's conclusion is valid because the sample was random. d. jeffery's conclusion is not valid because the sample was biased since all of the students were eighth grade students.

With: label the vertices and all the elements needed. find x