Question 522621
Let
Present age of Sally = s
Present age of Niece = n


Sally is four times as old her Niece
s=4n.............(1)
In three years
Sally will be = s+3
Niece will be = n+3
Then, Sally will be 3 times as old as her niece
s+3=3(n+3)
s+3=3n+9
s=3n+9-3
s=3n+6 ..............(2)

Put the value of s from (1) to (2)
4n=3n+6
4n-3n=6
n=6

Put the value of n in (1)

s=4n
s=4*6
s=24



Present age of Sally = s= 24 years old
Present age of Niece = n = 6 years old