I think you may be misreading the question, but it's so poorly worded it's hard to say. Where it says "create a formula that predicts the total number of coins if an unfair (weighted) coin is used that only comes up heads 1 out of every 4 times" I think what they really mean is "create a formula that predicts the total number of coins if unfair (weighted) coins areused that only come up heads 1 out of every 4 times." In other words ALL the coins are unfair, not just one. I think that if the meant that only one of the original 4 coins is unfair they would have written this as "create a formula that predicts the total number of coins ifoneunfair (weighted) coin is usedamong the first 4that only comes up heads 1 out of every 4 times."