To check equality we can try transform info correct form.
First, we can take 12 in front of parenthesis.
12m+12n=12(m+n)
We can do this because factor in front of paranthesis mean that all argument from paranthesis are multiplied by this factor.
We cant say that 12m+12n is equal to 12mn because we cant multiply \(m*n\) here.
12m-12n is not correct too.
