Given: Let b = Total number of books.
Total shelves = 5
Number of books on each shelf = (Total number of books) ÷ (Total shelves)
= b ÷ 5
The required expression for the number of books on each shelf =
4(2d + 5) = 8d + 20
15x + 18y = 3(5x + 6y)
I believe but I'm not quite sure, I believe that the correct answer would be 42 because by subtracting 79-37, that should give you y.
Hope this helps. (forgive any errors.)