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).
Where is the graph but in this case the y intercept would be -2 and you slope is 6 so go up 6 and to the right one and go down six and to the left one and thats what the graph should look like