Choice (A) Let the total work be of 900 units, thus Somesh does 20 units per day, Tarun does 15 units per day and Nikhil does 12 units per day. Since all three started the work together, the number of units completed in first 5 days=(20+15+12)×5=235units. The remaining work will be 900 – 235 = 665 units. Further, it is menioned that Nikhil left after 5 days and Somesh left 2 days before completion thus, for last two days Tarun was working alone and the work completed by him in last two days will be 15×2=30 units. The remining work 665 – 30 = 635 units will be completed by Taun and Somesh.
Therefore the total time in which the work will be completed will be