Prep PS one question

In a certain board game, a stack of 48 cards, 8 of which represent shares of stock, are shuffled and then placed face down.  If the first 2 cards selected do not represent shares of stock, what is the probability that the third card selected will represent a share of stock?

题是什么意思啊？怎么解答？

多谢

就是说有48张牌，其中8张要你share of stock，然后现在你先抽了2张，都没share of stock，（说明你没抽到那8张牌），问你抽到第三张牌要share of stock概率

所以应该是8/（48-2）= 4/23