Chapter 12 Sequences and Series - 12.3 Analyze Geometric Sequences and Series - 12.3 Exercises - Quiz for Lessons 12.1-12.3 - Page 817: 3

1/12, see below

The Numerators form a pattern; they are simply $n$. The denominators form a pattern too; they are the multiples of 10, starting with 20. Thus, the nth term is the combination of the two. $a_n = n/(10+10n)$ The next term will be... $a_5 = 5/(10+50)=1/12$