Question

The difference of a number and 12 is 4

Answer 1

We have two cases:
1. $12-?=4$
2. $?-12=4$

The first case will give you the answer of 8 (since 12 - 8 = 4).
The second case will give you the answer of 16 (since 16 - 12 = 4).

Answer 2

16, since the inverse operation of subtraction is addition add 12 and 4.