Explanation:

- Tap A can fill the tank in 6 hours, meaning it fills $\frac{1}{6}$ of the tank in 1 hour.

- Tap B can fill the tank in 8 hours, so it fills $\frac{1}{8}$ of the tank in 1 hour.

- Tap C empties the tank in 12.5 hours, which means it empties $\frac{1}{12.5}$ or $\frac{2}{25}$ of the tank in 1 hour.

- Working together, the net fill rate of the taps combined is:

- $\frac{1}{6}+\frac{1}{8}-\frac{2}{25}$

- This equals $\frac{50}{300}+\frac{37.5}{300}-\frac{24}{300}=\frac{63.5}{300}=\frac{127}{600}$.

- To half-fill the tank, which means filling $\frac{1}{2}$ of the tank:

- Time required = $\frac{1}{2}÷\frac{127}{600}\approx 2.36$ hours.

- Given options:

- Option 1: 2.1 hours

- Option 2: 2.4 hours

- Option 3: 2.7 hours

- Option 4: 2.9 hours

- Option 5: None of these

- The approximate nearest option is 2.4 hours.

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