2/57
or
0.0351
Since there are 19 total jerseys, the probability of grabbing a medium jersey the first time is 4 out of 19. This means that there is now one less jersey in the box, and we are assuming that the first one that was grabbed was a medium size. Therefore, the probability of grabbing a medium jersey the second time becomes 3 out of 18. We can multiply the probability of both events to find the probability of randomly grabbing 2 medium jerseys.
(4 / 19) * (3 / 18) = 2 / 57