It's not hard if remember a couple of things that you should have learned \before you ran into this problem. Here they are:
1). ' 10% ' means 10/100 , or 0.1
2). In middle school math,"of" almost always means "times".
Now that you know those two things, you can use them to re-write the problem:
" 10% of 120 " means " 0.1 times 120 ".
I'm sue you can solve that.
