A can do a piece of work in = 6 days
B can do a piece of work in = 12 days
C can do a piece of work in = 24 days
∴ A’s 1 day work = 1/6
∴ B’s 1 day work = 1/12
∴ C’s 1 day work = 1/24
(A + B + C)’S 1 day work = 1/6 + 1/12 + 1/24
= (4 + 2 + 1)/24 = 7/24
∴ (A + B + C) can do the work in = 24/7 days
= 3. 3/7 days