Exercise 2.5.2: Proof by contrapositive of statements about integer division. About Prove each statement by contrapositive (a) If x and y are integers such that 3xy then 3x. Solution (b) For any integers x, y, and z, if x|y and xz, then x(y z). (c) If x and y are integers such that x > 1, and x divides y, then x(y 1).