With these three math i really need it

1. is 9
and the other ones i dont really know

2.  replace the x by 2  and work it out 
= 7(2) - 5

3.  that cost $7.50 each  and $0.25 is taken off the cost of  any number you perchasse

so it 0.75n - 0.25

4.  Hint  the  second  (y) values are obtained from the first (x) values by multiplying  by 2

Quartile are numbers used to divide a set of data into four equal parts or quarter