Final answer:
To make up the loss of $100, Hannah and Dario need to sell 10 black t-shirts.
Step-by-step explanation:
To determine the number of black t-shirts Hannah and Dario need to sell to make up the loss in profit, we need to know the amount of the loss and the profit per t-shirt. Let's assume that the loss is $100 and the profit per t-shirt is $10.
To make up the loss of $100, they need to sell $100 / $10 = 10 black t-shirts.
Keywords: black t-shirts, sell, make up, loss, profit