Final answer:
Shawn must sell at least 15 shirts in order to earn at least as much as Nick.
Step-by-step explanation:
In order for Shawn to earn at least as much as Nick, we need to find the number of shirts, x, for which their earnings are equal.
Shawn spends $750 on supplies and charges $35 per shirt, so his earnings can be represented as: EarningsShawn = 35x - 750.
Nick, on the other hand, spends $600 on supplies and charges $25 per shirt, so his earnings can be represented as: EarningsNick = 25x - 600.
To find the number of shirts for which Shawn earns at least as much as Nick, we need to set up an inequality and solve for x. The inequality is: 35x - 750 >= 25x - 600.
Simplifying the inequality, we get: 10x >= 150.
Dividing both sides by 10, we find that x >= 15.
Therefore, Shawn must sell at least 15 shirts in order to earn at least as much as Nick.