I am rewriting using proper math input and slightly correcting
$dp/dt = rp$
a-b) Find the rate constant $r$ if the population doubles in 30 days.
\begin{gather*}
\ln p = rt + \ln C,\\
p = Ce^{rt},
\end{gather*}
The rest of your post is rather incomprehensible. To have it to multiply by $N$ in $T$ days we need to have $p(T)/p(0)= e^{rT}=N$ and then
\begin{equation*}
r=T^{-1}\ln N
\end{equation*}
Please fix your Name!