b=3
I found this out by subtracting and adding on both sides.
To start, find your equation, n=3000(.5)^t, n being your number of bacteria and t being your time. Now plug in 375 for n and solve for t, 375=3000(.5)^t, .125=.5^t,

. This means your answer is 3 minutes. To check it, plug it into your equation. n=3000(.5)^t=3000(.125)=375
Answer:



This might not be correct though. I'm only in middle school lol. I am sure about the last one.