Taking two discounts off (2 activities)

Memorial Day is a time for sales.  Advertisers want your business.  They often use repeated discounts to make you think you are getting stuff for free.  Be aware!      Double Discounts - Wow, check out this sale!  I'm gonna be able to get this great hoodie so cheap!   If I use the promo code what will be the total percent off?  

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Wow, everything must be free! -  What happens when you take 50% off again after taking 50% off at first?  Could everything be free?