The error message told you exactly where the problem is.
NoMethodError in Store#display_cart
Showing app/views/store/display_cart.rhtml where line #5 raised:
undefined method `product’ for 5.0:Float
Extracted source (around line #5):
Of course I always blaze right by that too
This forum is not affiliated to the Ruby language, Ruby on Rails framework, nor any Ruby applications discussed here.