Chapter 10 - Section 10.2 - Arithmetic Sequences - Exercise Set - Page 1059: 28

General equation is: $a_n=6+3(n-1)$; $63$

Formula to calculate the nth term of an arithmetic sequence is: $a_n=a_1+d(n-1)$ Here, $a_1: $ First term and $d=$ common difference Since, we have $a_1=6$ Then, our General equation is: $a_n=6+3(n-1)$ $a_{20}=6+3(20-1)=6+57=63$