Can anyone explain to me "subtraction by addition" in a visual way?
The steps say:
- Take the "complement" of the number we are subtracting
- Add it to to the number we are subtracting from
- Discard the extra "1" on the left
Example: $9 - 7$
- $7$'s complement is $3$
- Therefore $9 + 3 = 12$
- We discard the $1$ on the left and the answer is $2$
I don't understand how it actually works. Please help me to understand it.