I agree with ZOMBIE0O That the question is somewhat confusing. I see two options as being possible, depending on the nature of the question. The first option, 49, is a possibility. This would be the answer if the second two numbers were insignificant to the number of books (for example, if it were describing the dimensions of the books as 5•40). The second option is also a possibility, if the question is wanting you to add (49•5)+(5•40).
