Find s12 for the series 2 + 5 + 8 +

Hi, I'm pretty sure by S12 you mean the sum of all the 12 terms in the series 2 + 5 + 8 +

Then, first you find the pattern:
5 -2 = 3
8 -5 = 3
This is an arithmetic series with a common difference of 3. Next, we find the last term, or the 12th term.

A12 = A1 + (n - 1)d
A12 = 2 + (12 - 1)3
A12 = 35

Since, we know the first and last terms of the series, we could find the sum by this formula:

S = (n/2)*(A1 + A12)
S = (12/2) * (2 + 35)
S = 222

The answer is 222.

In all honesty, there really is no “work” per say to show. mainly it’s just using the process of elimination. the question is asking which domain(s) would be the most appropriate for the function c(n). n is the number of observed vehicles so right away, 1, 2, and 3 can be eliminated.why? 1, 2 start in the negatives and therefore it is impossible to observe negative cars. so, #4 would be the best answer to the given problem.

Did u want to find the value of x?