I own the comics that contain the top and bottom images. I really wish I had sold some of those off while they were worth something. Are comics worth anything these days?
I used to own Incredible Hulk 181. I was in Jr. High and a kid that was kind of a degenerate, but I used to play Shadowrun with stole it from Lonestar Comics. He was desperate for lunch one day and traded it to me for my lunch. At the time it was worth about $40, so another friend convinced me to trade it back to Lonestar so he could buy a box of D&D trading cards. He then gave me all his duplicates plus $40. I thought I got a good deal.
This is flawed. There needs to be an "if" at the beginning. "If you pick a box at random and pull out a gold ball then what is the probability of the second ball also being gold."
The way this pic is worded tells you that you already chose one gold ball. The probability of finding that first gold ball is moot. The situation as described is "You have a gold ball in hand and one unknown ball in the box" THAT is the starting condition of the question.