Discrete Mathematics for CS

I am hoping you can give me the reason why the answers are the way they are in detail, like a proof or a counterexample please. Thanks!

2t. Let the universe of discourse be Z+, the set 1, 2,3,... of positive integers. Let P(r, y,z) denote the statement "z is a multiple of rty" or, equivalently, "There is a positive integer q such that z (x + y)g" 8 pts What is the truth value of each of the following? You get +2 points for each correct answer, -2 points for each wrong answer, and 0 points for "don't know." However, the total for this question w not be less that 0 (a) Va3y22P(x, y, z) False True Don't know! (b) VyvzarP(, y, z) False True Don't know! (c) VrVyazP(r, y, z) False True Don't know! (d) V23r3yP(x,y, 2) False True Don't know