A, B and C can do a work separately in 18, 36 and 54 days, respectively. They started the work together, but B and C left 5 days and 10 days, respectively, before the completion of the work. In how many days was the work finished?

Answer: Option B

If B worked 5 days more = 3 × 5 = 15 unit
If C worked 10 days more = 2 × 10 = 20 unit
Now, total work = 108 + 15 + 20 = 143
(A + B + C) = $$\frac{143}{11}$$ = 13 days