Iforgot how to solve for x. 10x-8=9x+4

You need to get all the x-values to one side and all the non-x-values to the other by stepping it through like this:

10x-8=9x+4

1. add the 8 to both sides.
10x-8=9x+4
     +8     +8
10x=9x+12
2. subtract the 9x from both sides.
10x=9x+12
-9x  -9x
X=12

And your final answer is X=12 !
I hope this makes sense and helps! :)