A,B,C can do work in 36 days,52 days and 72 days respectivly.All three began the work together but A Left 8 Days and B left 12 days before Completion of work.How many days in all did C put in till the entire work was finished????

Let the total number of days taken to complete the work be T

So, C worked on all T days, A worked on T-8 days and B worked on T-12 days.

Hence, the total work done is T/72 + (T-8)/36 + (T-12)/54 = 1

Simplifying, we get 3T + 6T + 4T = 216 + 48 + 48 = 312
Or 13T = 312 and hence T=24 days.