I know how to put them in greatest to least, but does anybody have a trick to remember how to quickly get the answer?
I know when I'm tutoring students in addtion and subtraction of positive and negative numbers I always have them use a numberline. That way, if I say what is $\displaystyle -2+5$ it would look something like this:
<---(-3)---(-2)---(-1)---(0)---(1)---(2)---(3)--->
Then I have them put their finger at -2 and count 5 spaces to the right (since we are adding) and see where they end up. Which would be positive 3. Therefore, $\displaystyle -2+5=3$