Kate: Father : Age difference (different must be same, age different will not change throughout all the age)
In 5 years time
Kate: Father : Age difference = 1:3:2
Kate: Father : Age difference = 5:15:10
4 years ago
Kate: Father : Age difference = 1:6:5
Kate: Father : Age difference = 2:12:10
Now, the age different is same = 10
Kate 5u-2u = 5+4
3u=9
u= 3
In 5 years time
Kate: Father : Age difference
5u:15u
Total age = 20u
= 20 x 3
= 60
Therefore, their total age now
= 60-10 ( 5 years each)
= 50.
Mean Kate 10 years old , his Father is 40 years old.
Hope this helps