I'm 58 and I'm afraid my math skills are not what they used to be. I have been working on this problem for days now and have the correct answer, but only by trial and error. I'm working on a spreadsheet that will calculate a discount off a base price. All I have is the total price, which includes a service cost of .006 of the base price + a 15% tax on the service cost. In order to do this I need to know the base price. Since the total price includes the 15% tax, I need to be able to calculate the tax amount, deduct it and then calculate the service cost. How do I calculate the tax before I know the base price or the service cost? This is the best as I can represent it in a formula: x = 998,500 - (.15y) y = x/1.006 Any assistance would be appreciated.