Question 1
There are two stores,
and
, which sell t-shirts on the market. The store
has stock of
red and 2 black t-shirts and the store
has a stock of 2 red and
black t-shirts. One of the stores is selected at random and two t-shirts are purchased without replacement from that store. Given that both the t-shirts purchased are red, the probability that they were purchased from store
is
, find the value of
.






