Answer:
<em>It will take 12 hours to fill the tank</em>
Step-by-step explanation:
Proportions
Tap A fills a tank in 4 hours. It means each hour it fills 1/4 of the tank.
Tap B fills the tank in 3 hours. Each hour it fills 1/3 of the tank.
Tap C empties the tank when full in 2 hours. Each hour it empties 1/2 of the tank.
Each hour, the tank gets filled by:
Since the tank fills 1/12 of its capacity in one hour, it follows that it will take 12 hours to fill the tank