Explanation:

A's share after 7 years = B's share after 9 years

A(1+ 4/100)^7 = b(1+ 4/100)^9

A/B = (104/100)^2 
A/B = 676/625
?∴ A's share : B's share = 676:625
Since the total present amount is Rs 20,816
A's share = 20,816 × 676/(676+625)

=> 20,816 X 676/(1301)
 
=Rs.10816
B's present share = 20816-10816=10,000 rupees.