Someone wants to buy an item that costs $100. They have three stacking discounts of 20%,5% and 10% - for a total of 35% off. They add the items to their cart, they apply the discounts, but instead of the expected price of $65 their total comes out to be $68.40 before any taxes or shipping charges. They called the support line and are told the calculation is accurate - what happened?

A friend of theirs had two stacking discounts - of 25% and 10%, and got a different price - also not $65, but not $68.40 - what was their price?