Answer:
equation = $10*x - $100
Explanation:
Profit = earning - costs
Heidi has a cost of $100 either she sells 0 or she sells 30 toys. So, cost = $100 (for the case she made 30 units)
Earnings depend on how many units she sells, if she sells 1, she would earns $10; if she sells 20, she would earns $10*20 = $200; generally, earnings = $10*x, where x is the number of toys sold.
Profit for x number of stuffed toys sold = $10*x - $100