12+4 =x so you would add 12=4 to get 16. or x=16
I believe the answer is they are drawing an Octagon because a polygon has 5 sides add that by three it's an Octagon
The sum of n terms is given from the first term and the common ratio by

For your given values of a1=-11, r=-4, n=8, the sum of 8 terms is
