1/5N+3=6
1/5N-3=6-3
1/5N=3
Now, if you have 1/5 (one of 5 parts) of N and you need a whole N for your problem, you mutiply by 5, which in a fraction will be 5/1. 1/5x5/1=5/5, or 1 whole.
1/5Nx5/1=3x5/1, convert 3 to fractional 3/1, and multiply.
5/5N=15/1 then simplify to 1N=15, or N=15. Hope this helps!!