Is the question as posted correct? Is there a typo? All the informations are in?

Because if the posted question is correct, then here is a possible solution.

If he sold 5 eggs for Rs. 10, then each egg is sold for 10/5 = Rs. 2.00

If profit is 20%, then Rs. 2.00 is 1.20 times the cost of an egg.

So, 2.00 /1.2 = Rs. (1 and 2/3) per egg the man bought.

And if he had Rs. 10 to buy, then,

10/(1 +2/3)

= 10 / (5/3)

= 10 * 3/5

= 30/5

= 6 eggs he bought for Rs.10. -----answer.