for Quantity A:
The average (arithmetic mean) of 10, 20, and 30: They are consecutive numbers.
As we know that in Consecutive numbers the median is the average.
So median of Quantity A is 20 which means avg is also 20.
for Quantity B:
The average (arithmetic mean) of 12, 20, and 28.They are also consecutive numbers.
As we know that in Consecutive numbers the median is the average.
median of Quantity B is 20 which means avg is also 20.

so option (C) as both quantities are equal

Theory

➡ Average = Sum of all the Values / Total Number of Values
➡ Sum of All the values = Average * Total Number of Values

Quantity A: The average (arithmetic mean) of 10, 20, and 30

Average = \(\frac{Sum}{3}\) = \(\frac{10 + 20 + 30 }{3}\) = \(\frac{60}{3}\) = 20

Quantity B: The average (arithmetic mean) of 12, 20, and 28

Average = \(\frac{Sum}{3}\) = \(\frac{12 + 20 + 28 }{3}\) = \(\frac{60}{3}\) = 20

Clearly, Quantity A = Quantity B = 20

So, Answer will be C.
Hope it helps!

Watch the following video to Learn the Basics of Statistics