The third and fourth terms of a geometric sequence are 12 and 18, respectively. What is the first term of the sequence?
The common ratio is 18 /12 = 3/2
And we can solve this
(first term) (common ratio)^ ( 3 -1) = 12
(first term ) (3/2)^(3 - 1) = 12
(first term) ( 3/2)^2 = 12
(first term) (9/4) = 12
first term = 12 (4/9) = 48/9 = 16/3
