Answer: The boots were marked $86.
Step-by-step explanation: We know Mica's total was $100 for the bill. He got the only hat left marked $12, and a pair of boots. Before tax and after a 50% sale, her total is $100. Since she spent $12 for the hat, we know the rest of the money is going towards the boots. The boots will cost $86.
Hat($12) + Boots($86) = 100