I'm a commission sales person and I need help with a simple formula. I sell furniture and on that furniture I can sell a protection plan I get paid different commissions on the two products. I get paid on the total amount of furniture sales less the dollar amount of the protection. Now my commission rate on my protection is based on the percent of protection I have sold on my furniture sales. Ex. If I sell a dollar amount equal to 7.5% of furniture sales I get 30% of the protection dollar amount. How would the correct % of protection to furniture be calculated ? Let's say my total sales furniture plus protection is $115,000 and my protection amount is 8,000 my furniture sales amount is 107,000