What is the missing term in the geometric sequence 3/4 1/2 1/3?

Missing where?  Is it possible that you meant, "What is the next term of the geom. seq.  3/4, 1/2, 1/3,    "? 

First term, a(1), is 3/4.  How do we get 1/2 from 3/4?  Divide:

   1

   2          1       4
= * = 4/6, or 2/3.  Check this out:  r=common factor= 2/3.
  3           2       3
 
   4

Do we get 1/3 when we multiply 1/2 by 2/3?  YES.

Written formally, a(3) = (3/4)(2/3)^(3-1)  =  (3/4)(2/3)^2  =  (3/4)(4/9) = 1/3

What's the next term (the missing term)?

a(4) = (3/4)(2/3)^(4-1) = 2/9 (answer)

The second and fourth answer are correct