Final answer:
Winston's 7th charge is $41.15, found by subtracting the sum of the known 6 charges from the total amount spent on all 7 charges, given the mean charge per transaction.
Step-by-step explanation:
To determine the amount of the 7th charge on Winston's credit card statement, we first need to find the total amount spent on all 7 charges. Since we know the mean charge is $34.00 and there are 7 charges, the total spent is 7 times that mean, which equals $238.00 (7 times $34.00). Next, we sum the known 6 charges: $33.78 + $34.24 + $35.59 + $29.88 + $36.58 + $26.78 equals $196.85. Now, we subtract this sum from the total to find the unknown 7th charge: $238.00 - $196.85 equals $41.15.