Dear Student,
Let Sumit's mother's age be x yrs.
Then Sumit's grandmother's age = x + 22 yrs
And, Sumit's age = x - 27 yrs
Also, Sum of their ages = 121 yrs
Then, x + x + x + 22 - 27 = 121
3x -5 = 121
3x = 126
x = 42 yrs
x - 27 = 15 yrs
Sumit age is 15 yrs.
Regards..