klvin is 21 year old and his sister is third is age . when kalvin is 36, what will be the age of his sister?

klvin is 21 year old and his sister is third is age . when kalvin is 3

1.	klvin is 21 year old and his sister is third is age . when kalvin is 36, what will be the age of his sister?
Answer» is 21 then his SISTER is 3 then when he is 36 his sister is 18