Answer: 7,864,320
Step-by-step explanation:
Because the doubling time is 20 minutes, the bacteria would have gone through binary fission(cell division in bacteria) 18 times after 6hours(6*60/20)
Nt=N0 * 2^n
N0=starting population
n=number of times bacteria divide
So
30*2^18=7,864,320