No, as you want to subtract only that case where no topping will be there, multiplying by 2 signifies that the topping is there and topping is not there so if all fall in not there category then our condition in q fails so we subtract 1, you probably be getting confused by the fact that since a particular topping is not there so subtract it and since there are 10 so do minus 10 but the problem with that reasoning is that it doesn’t eliminate the case that there will be other toppings
No. There are 10 flavours after all, so 10 ways to have an ice-cream without toppings.
The OP is correct, but we already made a note below the video.