Question

What would the sum of -18-(-12) be?

Answer 1

-18-(-12)=-6 
Since there is two negative sign, it turns into positive meaning the -12 becomes positive 12 and the -18 stays same. So -18+12=-6 because 18 is bigger than 12 and it's negative so the final answer should be negative. 
Hint: when you see two negative sign just turn them into plus sign.  

Answer 2

-18-(-12)= -18+12 = -6
Since (-*-)= + sign
So -18+12 will be equal to -6