-1/2 ans. Hope it helps..
Answer: -4.775
Step-by-step explanation: 11(7/8) + 3(1/5) - (-4.775) = 15
3 pipes take 12 hours
⇒ In 1 hour, the 3 pipes can fill 1/12 of the pool
2 of the pipes take 18 hours
⇒ in 1 hour, the 2 pipes can fill 1/18 of the pool
In 1 hour, the third pipe alone can fill :

Time needed :

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Answer: It will take 36 hours for the third pipe to fill the pool.----------------------------------------------------------------------------------------
The answer would be 4,069.40