Answer:
t = (ln 1,000,000,000)/ (ln 5)
from equation: Â 1,000,000,000 = 5^t
or you can translate: Â t = Â log of 1,000,000,000 with base 5
Step-by-step explanation:
We see the equation is  P =  5^t
where P = the number of bacteria
t = days
t = 0 day  we see P = 5^0 = 1 bacteria
so...
now you want t  when P= 1,000,000,000 bacteria
1,000,000,000 = 5^t
solve for t
t = (ln 1,000,000,000)/ (ln 5)