Note: I just noticed that you only have one negative sign. If you mean to put -9, change the sign to positive. If not, leave the answer.
Note the equal sign. what you do to one side, you do to the other. Isolate the x. First, multiply 3 to both sides
-x/3(3) = 9(3)
-x = 9(3)
-x = 27
Next, to isolate the x, divide -1 from both sides
-x/-1 = 27/-1
x = 27/-1
x = -27
-27 is your answer for x.
hope this helps