#### Answer

common difference;
$2$;
$5$

#### Work Step by Step

RECALL:
The $n^{th}$ term $a_n$ of an arithmetic sequence can be found using the formula:
$a_n = a + (n-1)d$
where
$a$ = first term
$d$ = common difference
$n$ = term number
Thus, the missing expressions in the given statements are (in order):
common difference;
$2$;
$5$