Chapter 7 - Section 7.2 - Arithmetic Sequences and Series - 7.2 Exercises - Page 645: 1

$d=3

$\bf{\text{Solution Outline:}}$ To find the common difference of the given arithmetic sequence, $ 2,5,8,11,... ,$ subtract a term by its previous term. $\bf{\text{Solution Details:}}$ Since the common difference of an arithmetic sequence is the difference between a term and its previous term, then with $a_2= 5 $ and $a_1= 2 $, the common difference, $d$, is \begin{array}{l}\require{cancel} d=5-2 \\\\ d=3 .\end{array}