Answer: 80 minutes.
In 24 hours:
- the cold tap could fill 72 baths
- the hot tap could fill 48 baths
- the plug could drain 90 baths
- the leak could drain 12 baths
Therefore, in 24 hours, we have 72 + 48 - 90 - 12 baths full = 18 baths.
Therefore each bath would take 80 minutes to fill.