Ihave a homework about subtracting integers and i don't get what -9 - 5, 31 - 48, ang -6 - 7 is

Well remember this:
When the signs are the same it is positive
When the signs are different make it negative

When you are subtracting a negative and positive, it is going to be like adding
for example:
-9 - 5 = -14
You just add 9 and 5 to get 14, the signs are different so it is going to be negative. ONLY WHEN YOU ARE SUBTRACTING NEGATIVES