I believe the answer is the second one
The wording of this question is a bit confusing... You can't write a sequence in sigma notation, but rather a series or sum. I think the question is asking you to write the sum of the sequence,

which would be

in sigma notation.
To do this, notice that the denominator in each term is a power of 2, starting with
and ending with
. So in sigma notation, this series is

Answer:
There are 9 adults
Step-by-step explanation:
3:5 = x:15
3/5 = x/15
3(15) = 5x
5x = 45
x = 9 adults
3:5 = 9:15
The number is -11/4 less than -8/3