Question

the difference between a number and 12 is 20

Answer 1

two possible answers
 32
or if you have negative numbers
-8

Answer 2

We shall call this number "n".
1.n-12=20

First, we move our 12 over to the 20.

When a number crosses over the = signs it changes signs.

So, we'd be adding 12 to 20.
n= 32
There's your answer.