Answer :
-1 is the answer because if you go back on a number line you will get -6.
You're solving for x.
x - 5 = -6
x - 5 + 5 = -6 + 5
x = -1
-1 - 5 = -6
x - 5 = -6
x - 5 + 5 = -6 + 5
x = -1
-1 - 5 = -6