12) A movie on-demand service charges an 18$ monthly fee. It also charges a 3$ fee per movie rental. If Nathan rents 20 movies in a year, how much would the service cost?

216

Step-by-step explanation:

18×12=216

I'm not sure if this is what the question means but theres 12 months in a year and its 18 per month

arithmetic sequence: a sequnce in which the diffrence between any two consecutive terms is the same

step-by-step explanation:

(n^3 - n)

= n(n-1)(n+1)

since it is divisible by 3 and 2 ,because it is a multiple 3 consecutive number

if, n-1 is odd then n+1 is also odd, then it is a multiple of 9

but if, n-1 is even then n+1 is also even, then it is a multiple of 4

so, largest multiple = max(9*2, 4*3) = max(18, 12) = 18