Final answer:
To find the regular admission price for one adult, the total cost paid by the 6 adults after using the coupons is calculated, and then divided by the number of adults. The regular admission price for one adult is $12.50.
Step-by-step explanation:
To find the regular admission price for one adult, we can start by finding the total cost paid by the 6 adults after using the coupons. Since each person has a coupon for $5 off, the total amount saved is 6 * $5 = $30. So the total amount paid by the 6 adults is $105 - $30 = $75.
To find the regular admission price for one adult, we divide the total amount paid by the number of adults. Therefore, the regular admission price for one adult is $75 / 6 = $12.50.
Thus, the correct answer is D) $25.