When you subtract from a negative it becomes a bigger number in the negatives. Subtract from a negative is also kind of like adding the 2 numbers then making it negative.
<u>Example:</u>
-2 - 2 = -4
2+2=4 making it negative will give you the answer of -4
-9-10 is like 9+10 which equals 19. Making it negative will give you the answer of -19
