Explanation:
I don't know if you do this the same way I did, but..
The first step is to subtract 9 on both sides, like this.
13w + 9 = 178
-9 -9
You'll end up with:
13w = 169
I don't know if you need the answer or not but I'll help you out.
For the second step, divide both sides by 13w.
13w = 169
/13w /13w
w = 13
Hope this helped!