Astore offers a 15% discount on all items in the store during a sale. all store employees get an additional 10% employee discount . in the equation below, c represents the cost of an item for an employee including tax and x represents the original price of the item :
c = 0.765x + 0.06(0.765x)
chris is an employee at the store he plans to buy a coat during the sale . the price of the coat before the discount is $100. how much will chris pay for the coat during the sale? remember, do not include the $ symbol

0.765 (100) + .06 (.0765 x 100)
76.5  + .06 (76.5)  
76.5 + 4.59 = 81.09    Chris will pay $81.09

A better way ( if you don't care to know the tax just the bottom line of what it will cost) would be to do:

0.765x x 1.06 = 76.5 x 1.06 = $81.09 too.

Why the 1 in front of the .06?  The one includes the price of the coat so you don't have to add the tax on after.
Think about it like this. When you buy something you pay (even with an employee 
discount) for all of it (100%) + the tax (in this case, it's 6%)  So you pay 106% of the cost of the item.  106% = 1.06

The clear answer is clearly 25 is very clear to me