15-1/6n=1/6n-1
First, lets multiply both sides by 6 so that n is a whole number:
90-n=n-6
now you group like terms on each side, to do this you add n to each side and add 6 as well so it becomes:
96=2n
Now divide both sides by 2 so you have 'n' on one side and it is:
48=n
Hope this helps :)