Answer: -3
Step-by-step explanation: In this problem we are asked to subtract -6 - (-3). It's important to understand that when we have minus a negative, we can change it to plus a positive.
Now we have the following.
-6 + 3
Starting at 0 on our number line, -6 moves us 6 units to the left. Then from there, positive 3 moves us 3 units back to the right and we end up at -3.
Therefore, -6 - (-3) = -3