Answer:
This may be written incorrectly.
Assuming that this is written correctly, then we have that:
6 + 6 = 12
is equivalent to:
6 + 6 - n = 12
Here the properties that we can add 0 in one side of the equality and this does not change the equality, so this only works if n = 0.
If we instead had:
6 + 6 = 12
is equivalent to:
6 + 6 - n = 12 - n
In this case, Noah used the additive or subtractive property of equality.
this property says that in an equality we can add (or subtract) the same value on both sides, and it does not change the equality.
