Answer
$ a_{n}=4 +5(n-1)$ and $ a_{12}=59 $
Work Step by Step
We need to use the formula $ a_n =a_1+(n-1) d $ ....(1)
Here, $ a_1=4$ and $ d=5$
$ a_{n}=4 +5(n-1)$
Now, plug in: $ n=12$
$ a_{12}=4 +(12-1) \times (5) $
and $ a_{12}=4 +55 =59$
So, $ a_{n}=4 +5(n-1)$ and $ a_{12}=59 $
