I know this isn't answering your question but i think you will find it useful to visit the link pasted below. i just visited it and it explains pretty much everything about this.
The answer to 2-7 would be -5, but 7-2 would be 5, depends how specific one is trying to be.
Answer: Option C) Pluto
Explanation:
Pluto is described as a dirty ice ball of frozen gases and rocky material. It was the ninth planet to be discovered.
