Math Help - Implicit differentiation problem (I think?)

1. Implicit differentiation problem (I think?)

Rewrite the statement in mathematical notation (Let n be the number of cases of Bangkok flu and t be time.)
There are presently 350 cases of Bangkok flu, and the number is growing by 30 new cases every month.

n =
dn / dt =

I'm not sure how to even start this really. 350 + 30n but where do I go from there? Any help appreciated.

2. Let $a_n$ be the number of cases in month n.

$a_0 = 350$.
$a_{n+1} = a_n + 30$.

3. What's the actual question?