Answer:
12 years.
Explanation:
We have been given that the average 8 year old gets 30 questions right on an intelligence test, whereas the average 12 year old gets 50 questions right. We are asked to find the mental age of an 8 year old who gets 50 questions right.
Since the 8 year old boy gets 50 questions right and the average 12 year old also gets 50 questions right, so the mental age of 8 year old (getting 50 questions right) will be equal to the mental age of 12 years old.
Therefore, the mental age of an 8 year old who gets 50 questions right would be 12 years.