Explanation:
-3x-9
divide the equation by -1 so that the -1's are taken from -3x and -9. so the -1 goes on the outside of 3x+9
-1(3x+9)
then divide the equation by 3 since 3x and 9 is divisible by 3.
(-1)(3)(3/3x+9/3)
-3(x+3)
Now we can expand again to check the problem
-3 times x=-3x
-3 times 3=-9
and add
-3x-9
Hope that helps :)