Woman age is 24 and niece age is 8.
Solution:
Six years ago a woman was nine times the age of her niece
f-6 = 9(n-6)
f-6 = 9n-54
f-9n = -54+6
f-9n = -48 .............(1)
she is now three times the age of her niece.
f = 3n; .................(2)
Then, add (2) in (1)
f-9n = -48
3n-9n = -48
-6n = -48
n = 48/6
n = 8
Hence, n = 8 is niece age.
And n = 8 add into (1)
f-9(8) = -48
f-72 = -48
f = -48+72
f = 24
Hence, f = 24 is woman age