Chapter 5 - Number Theory and the Real Number System - Chapter Summary, Review, and Test - Review Exercises - Page 336: 130

$a_6=20$

Recall: The $n^{th}$ term ($a_n$) of an arithmetic sequence is given b the formula: $a_n=a_1+(n-1)d$ where $d$=common difference $a_1$=first term. Thus, for the given arithmetic sequence, \begin{align*} a_6=a_1+(6-1)d\\ a_6&=5+(5)3\\ a_6&=5+15\\ a_6&=20 \end{align*}