You want to sell t-shirts for $12 a piece. It cost you $40 for supplies. Is the total profit proportional to the number of t-shirts you sell?
Yes, the total profit is proportional to the number of t-shirts you sell. The profit per t-shirt sold is $12 minus the cost of supplies ($40). Therefore, for each t-shirt sold, the profit is $12 - $40 = -$28.
Thus, the total profit will be negative as long as the cost of supplies is greater than the total amount earned from selling t-shirts. So, if you sell one t-shirt, the profit will be -$28, if you sell two t-shirts, the profit will be -$56, and so on. Therefore, the total profit is indeed proportional to the number of t-shirts sold.