The final answer is 3.
Let's start with the initial representation of the number 6 using the + and - tiles:
+++++++++
- - -
a. 6−7:
Remove 7 tiles from the right side:
+++++++
- -
The final answer is −1.
b. 6−(−2):
Since subtracting a negative is equivalent to adding, we add 2 tiles to the right side:
++++++++++
- - -
The final answer is 8.
c. 6−3:
Remove 3 tiles from the right side:
+++++
- -
The final answer is 3.