Answer:
p = 5k - 40
Explanation:
Since we're finding the profit (p), it's not the last answer choice because it's finding kids (k).
Because we have to take out from her profit whatever Katie spent, we would have -40.
Because she'd charging $5 per kid, or $5 per k, we would have 5k.
So now we know the profit is whatever she makes, then minus whatever she spent. So:
p = 5k (what she makes) - 40 (what she spent)
p = 5k - 40