Let x = the number we are looking for:
Difference means that we subtract:
[tex]x-(-3)=6[/tex]
Two negative signs turn it into one positive sign (a plus):
[tex]x+3=6[/tex]
We need to get x by itself, so we subtract 3 from both sides:
[tex]x=3[/tex]
So now we know that the number we were asked to find is 3.