What does a minus plus a minus equal?

A minus and a minus (-4+-5) is a minus. It only becomes a plus if two minus's are timesed together.

eg. -4 + -5 = -9

-4 x -5 = 20

It is easier to work with if you have no negatives on the second number. You can switch the two symbols that are next to each other without disturbing the equation. For example:

-4 + -5= -4 - 5= -9

It makes it easier to trace on a number line. I hope this helps more than confuses