FIVE QUESTIONS are asked. Don't just give me one answer. I've recently received a slew of inomplete responses, which is extremely frustrating. Please don't squander your or my time. If you are unable to answer all of my questions, please disregard them. I don't want to squander my paid-for post-question time. Also, if you continue to give me incomplete answers, I will give you a thumbs down and will complain. Thank you very much.

1) Prove or disprove: if r and s are rational numbers, then (r+s/2) is rational.

2) Prove or disprove: for any rational numbers r,s (2r+(s/3)) is an integer.

3) Prove: a,b,c Z if a|b and a|c , then a|(b-c)

4) Prove:a,b,c,d Z if a|c and b|d then ab|cd