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let Deepak’s age be x

If Deepak’s age is x, then Dipti’s age will be 3x.

Rani is 4 years younger than Dipti, so her age will be 3x-4

Given, x+3x+3x-4 = 66

7x = 70

x = 10

Therefore, Dipti’s age will be 3*10 = 30 years