Examples of this are:
2 and 
2 and 
4 and 
I'm guessing you have a work sheet going along with this which has actual images of containers. I've attached an example - if you can post the actual work sheet you're referring to I can edit this answer to correctly reflect your specific question.
Answer:
n = 9
Step-by-step explanation:
20 + 18 + ... + 6 + 4
---------------------------
a = 20 ; d = -2 ; n = ?
--------
4 = 20 + (n-1)(-2)
-16 = (n-1)(-2)
---------
n-1 = 8
n = 9
-------
S(9) = (9/2)(20+4)
S(9) = 4.5*24
S(9) = 108
Answer:
482.84 cm
Step-by-step explanation:
#7
2,4,8,16
15,30,60,120
#9
1,2,3,
4,8,12
