Ageometric sequence is shown below:

A) Common Ratio (r) = -2

B) and

Explanation:

We are given a geometric series with some missing term.

Common ratio of geometric series is ratio two consecutive term.

Common ratio (r) =

Now we find the missing term.

First term of the series.

Common ratio r=-2

So,

So, a=5.5

Now we find second missing term . This 4th term of the series

So,

where, a=5.5 and r=-2

$12. that is my answer.