In ch 4 of the Algebra Strategy guide, I am not clear on when to switch the GT to a LT in a problem. On page 89-90, I follow the explanations on how to find a range with the largest and smallest values for a variable, but when they change from using Less Than or Equal to OR Greater than or Equal To...to just Less Than or just Greater than (LT or GT), I am not clear.
For example, on page 90, in the box, you have m Min is -4, n min is GT(-3) and then the problem m-n is shown as (-4)- GT(-3)=LT(-1).
On a GMAT Manhattan Prep site I found that sometimes you can substitute LESS or MORE for the < or >, and sometimes that helps you know the sign of the answer (i.e., Less - Less = Less, so -4 - LT-2 = LT-6
But there were some exceptions and I didn't follow the logic.
Is there an explanation somewhere, and will I need this for the GRE, since I found a partial answer on the GMAT prep page, but can't seem to find anyone who understands it either.
Thank you.