Answer: 8
Explanation:
A Geometric sequence can be used: 
To Model this sequence you need to use this formula 
A (subscript n) = Ar(n-1) 
a = value of the first term 
n = the # of the term you want to find (For example, if you want to find the term number 3, it is 12) 
r = the common ratio, this is obtained by dividing the second term in the sequence by the first. 
So the value of r is = 2/3 because 27 times 2/3 = 18 which is the second term 
n = 4 since you want to find the 4th term in the sequence 
Plug it in and results are 
4th term = 27(2/3)^(4-1) = 8