Verified answer

Step-by-step explanation:

We know that,

Number of days A requires to do piece of work =10 days

Number of days B requires to do the piece of work =12 days

Number of days C requires to do the piece of work =15 days

∴ We can calculate, work done by A in 1 day=1/10

Work done by B in 1 day =1/12

Work done by C in 1 day =1/15

Now, work done by A,B and C together in 1 day =1/10+1/12+1/15=15/60=1/4

∴ They can do work together in 4 days.