i need help with this question
A, B and C can do a work in 10, 12 and 15 days respectively. They begin the work together but after 3 days C left the work and 4 days before the completion of work B left the work. In how many days will the total work be completed?
this is a time and work question, and the teacher told us the answer should be 68/11 days, for the total work done. but that doesnt include the 3 days worth of work that a,b,c did together before c left right? so im confused whether it should 101/11 days or 68/11 days. please help!!