Answer
$a_n=3n-1$
$a_{51}=152$
Work Step by Step
We know that the $n^{th}$ term $a_n$ of an arithmetic sequence is given by the formula
$a_n=a_1+(n-1)d$
where $d$=common difference and $a_1$= the first term
Hence, here we have
$a_n=2+(n-1)3\\
a_n=2+3n-3\\
a_n=3n-1$
Therefore,
$a_{51}=3\cdot51-1\\
a_{51}=153-1\\
a_{51}=152$