Anthony takes 5 days more than Bastian to do a certain job and 9 days more than Catherine; Anthony and Bastian together can do the job in the same time as Catherine. How many days Anthony would take to do it?

Solution : 

Anthony  :  Bastin  : Catherine
X+9.              X+4.            X
W= √9*4= 6 
Anthony = 9+6=15 days Ans.