Question

-x-4=9 ( find the x )

Answer 1

X=-13 
Because 9 plus 4 is 13 but x can't be negative so you divide my negative 1 and get x=-13 

Answer 2

You need to make x the subject. This means only x needs to be on one side of the equals sign.
-x-4=9
you need to keep x positive so +x on both sides (because it is the opposite of minus)
-4=9+x
minus the nine on both sides (because it is the opposite of adding)
-11=x
This is the answer.
-11=x