So profit = revenue - expenses.
We know his profit was 160.00. We do not know the revenue that this book case generated and this is what we are trying to find.
160=X-647-.15X.
this comes out to
160=-647+.85X
take the 647 over by adding it to both sides and you get 807. Then divide 807 by .85 to solve for X which is the cost. and you get 949.41.