<PRE><B>Question 775331</B>
Edited to make more sense.
:
A can complete the work in 12 days
 B can in 15 days
 C can in 24 days (separately).
If A works for 3 days and leaves, and after A leaving, B works for 5days, and he also leaves, then C takes how many days to complete the remaining work?
:
let t = time required by C to complete the work
Let the completed job = 1
:
A shared work equation:
:  A  +  B  +  C  =  1
{{{3/12}}} + {{{5/15}}} + {{{t/24}}} = 1
Reduce the fractions
{{{1/4}}} + {{{1/3}}} + {{{t/24}}} = 1
multiply by 24 to clear the fractions, resulting in
6 + 8 + t = 24
t = 24 - 14
t = 10 hrs for C to complete the job </PRE>