Description for Correct answer:
Pipe A and Pipe B work for 8 minutes together and fill = \( \Large 8 \left(\frac{1}{24}+\frac{1}{36}\right)=\frac{5}{9} \)th of the tank

Pipe A, B and C will be able to fill \( \Large \left(\frac{1}{24}+\frac{1}{36}-\frac{1}{30}\right)= \frac{13}{360} \)th of the tank in a minute.

Therefore, the remaining \( \Large \frac{4}{9} \)th of the tank can be filled in \( \Large \frac{4}{9} \times \frac{360}{13} \) = 12.3 minutes

Totally, in 20.3 min. the entire tank will get filled.