Explanation
Let's break this down step by step:
The average age of seven members is 75 years, so the total age of all seven members is: 7 x 75 = 525 years
The average age of six members is 74 years and 6 months, which is equivalent to:
74.5 years (since 6 months is half a year)
So, the total age of these six members is: 6 x 74.5 = 447 years
Now, subtract the total age of the six members from the total age of all seven members to find the age of the seventh member: 525 - 447 = 78 years
The correct answer is: 78.