Andy has 9math books and 6reading books if he want to distribute them evenly among some bookshelf's so that each has the same combination of books with none left over what is the greatest number of bookshelves andy can use

The figure shows triangle def and line segment bc, which is parallel to ef: triangle def has a point b on side de and point c on side df. the line bc is parallel to the line ef. part a: is triangle def similar to triangle dbc? explain using what you know about triangle similarity. part b: which line segment on triangle dbc corresponds to line segment ef? explain your answer. part c: which angle on triangle dbc corresponds to angle f? explain your answer. asap