Answer
Formula for $a_{n}$ term of the given sequence = $a_{1}$ + (n - 1) d.
Where
$a_{1}$ = The first term
d = Common difference
n = $n^{th}$ number of term
Given
$a_{1}$, the first term = 9
Common difference (d) = 2
$20^{th}$ term of sequence = 47
Work Step by Step
Formula for $a_{n}$ term of the given sequence = $a_{1}$ + (n - 1) d.
Where
$a_{1}$ = The first term
d = Common difference
n = $n^{th}$ number of term
Given
$a_{1}$, the first term = 9
Common difference (d) = 2
$20^{th}$ term of sequence = 9 + (20 - 1) $\times$ 2
= 9 + 19$\times$2
= 9 + 38
= 47