8
7
11
10
Answer is Right!
Answer is Wrong!
The correct answer is (a) 8.
The mean is the sum of all the values divided by the number of values. In this case, the mean is 18, so the sum of all the values is $18 \times 7 = 126$. The class interval with the highest frequency is $10-19$, which has a frequency of 3. So the values in this class interval must add up to at least $3 \times 10 = 30$. The only value in this class interval that is less than or equal to 30 is 8. Therefore, the value of A must be 8.
Option (b) is incorrect because 7 is not a value in the class interval $10-19$.
Option (c) is incorrect because 11 is not a value in the class interval $10-19$.
Option (d) is incorrect because 10 is not a value in the class interval $10-19$.