He has 286 Fiction Books. Why? Assume number of Non Fiction Books to be x So, number of Fiction Books will be 11x The sum of both the books is 312 So, 11x + x= 312 12x=312 x=312÷13=26 x was the number of Non Fiction Books. So, there are 26 Non Fiction Books. Fiction Books= 11x=11*26=286. Hence, there will be 286 Fiction Books in Mark's bookcases.
