Write an explicit formula for the arithmetic sequence whose common difference is -18

Let the first term be a(0).  Then the formula for a(n) is a(0)-18(n-1).

Check:  What's the first term?  Let n = 1:  a(1) = a(0)-18(1-1) = a(0) (correct)

What's the second term?    Let -n =2:  a(2) = a(0)-18(2-1) = a(0) - 18

and so on.

we'll this would mean that the dunk tank and the bounce house are the same for 20 hours because the 2 represents that the two activities, and the 20 represents the amount of hours they both are. so with this said, it means that the answer is c. the costs for a dunk tank and bounce house are the same for 20 hours.

c.the costs for a dunk tank and bounce house are the same for 20 hours.

hope this .