n=4
With the equation use the distributive property to multiply 3 into (n+2). And 9 into (6-n).
Then you should have 3n+6=54-9n
You add 9n to both sides to get 12n+6=54.
After you should subtract six from both sides to get 12n=48
The last step is to divide 12 from both sides to get n=4 :)
