Notice that there are 12 units between -8 and 4:
In order to get 4 by adding or substracting a number from -8, we must add 12 units. Nevertheless, the sign that is set before the blank box is a negative sign. Remember that substracting a negative number is the same as adding its positive equivalent:
[tex]4=-8+12=-8-(-12)[/tex]
Therefore, the answer is:
[tex]-12[/tex]
