Hi bhavook :)
For Competitive equilibrium, the following two conditions should be satisfied:
1) Consumers are maximizing their utility ie. finding the demand.
2) Market clearing for all goods i.e demand = supply for both the goods.
In your question:
Both the consumers have "min" utility function so they will demand equal amount of good x and good y in equilibrium. But the quantity for good x (10 units) is more than the quantity of good y (5 units) available in the economy. Therefore, to clear the market, price of good which is available in abundance (here, it is good x ) should be zero.
:)