Deepa is twice as old as Kiran, and Kiran is 5 years younger than Malini. If Malini is 21 years old, what is the average age of the three of them?

Kiran is 21 - 5 = 16 and Deepa is $2\times 16=32$, so the three ages are 32, 16 and 21, totalling 69, and the average is 69/3 = 23 years. 33 reads the second clue backwards, making Kiran 26 and Deepa 52. 69 is the total, not the average. 21 is Malini's age; the middle value of three numbers is not in general their average.