Problem regarding bacteria increase modeled by formula

Question

Studying "Basic Mathematics" p.358, by Serge Lang, came across this exercise.

I don't know how to start with it. Any insight would be appreciated.

Answer 1

Hint:

First note that $C=B(0)=10^6$.

Next, you can rewrite this equation as $\;\dfrac{B(t)}{B(0)}=\mathrm e^{kt}$, and you have to find $k$. You're given that $$\frac{B(12)}{B(0)}=2. $$ WWhen ytou have $k$, you'll just have to solve $$\frac{B(t)}{B(0)}=10.$$ Can you end the calculations?

Answer 2

Try transforming your equation by taking the logarithm of both sides. What happens if you plot $log(B)$ against $t$? That should suggest several ways to solve the problem.