Explanation:

- To solve the problem, determine the efficiencies of A, B, and C. Their ratio is 4:5:3, so consider their efficiencies as 4x, 5x, and 3x respectively.

- Their combined efficiency is 4x + 5x + 3x = 12x.

- They complete the work in 25 days, which means they do 1/25th of the work daily.

- Set 12x equal to 1/25 to find x, where x = 1/300.

- A and C’s combined efficiency is 4x + 3x = 7x = 7/300 of the work daily.

- To find the days needed to complete 35% (0.35) of the work, calculate 0.35 / (7/300) ˜ 15 days.

- Option 4: 15 days is correct.

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