Answer:
k = 8 + 100 (.25) - 2x
Step-by-step explanation:
Since there's a flat shipping rate, you need to first add 8.
Then you have to pay for the 100 key chains at $.25 each so you have to multiply them to get the total cost.
Next you earn 2 dollars for every key chain sold which becomes the 2x. You are then subtracting this from the amount of money you are spending to get k.