4 shelves the first three shelves can hold 8 books each and the fourth shelf has 3 books on that shelf so altogether 4 shelves for 27 books
To simplify a fraction by division you must have common factors between the denominator and the neominator to divide (or cancel) them
X = 3 / 2
y = 17 / 14
z = 41 / 14
If you need to see me work it out, let me know.