Ratio of present age of A and B is 7 : 13 . After 6 years the ratio of age of B and C will be 5 : 3. If the present age of C is 21 years, then after 3 years age of A will be:

24 years  

Present age of C = 21

After 6 years C's age = 27

ATQ, after 6 years ratio ⇒      B : C = 5 : 3

⇒ 3R = 27

⇒ 1R = 9

⇒ B's age after 6 years = 5R = 45

⇒ Present age of B = 45 - 6 = 39

Now,

Present age of A and B ⇒ 7R and 13R

⇒ 13R = 39

⇒ 1R = 3

⇒ A's present age = 7R = 21

⇒ After 3 years age of A = 21 + 3 = 24 years