If 9kg costs 12$, then a single kg costs around 1.3$
This is done with a simple proportion
9 : 12 = 1 : X
x = 12/9
x = 1.33
84/3=28
The 3 consecutive numbers would be 26,28,and 30
It looks like you have to do distance formula. It's basically this:
D =
(ignore the A, i dont know how to get rid of it sorry)
I would then plug in the points of A(1,7) and B(10,3).
D = 
Then I would get the square root of 4^2 + 9^2
= square root of 16 + 81
= square root of 97
So the length of AB would be the square root of 97
118/13= 9 1/13
She will need 10 boxes. There will be 1 basketball in box 10.