Can somebody help me to answer this question?

If the stocks in terms of goods, then the entries are
Debit stock
Credit capital

If in terms of money or cash,
Debit cash or bank account
Credit capital account

- good luck:)

what is the equation for closing stock

Mr nabelle your answer is no way related to the question
The true answer is
Trading a/c dr
To closing stock a/c
The inventory will be always on debit side it is the fundamental rule .To close it we have to make a reverse entry.

The equation for closing stock is
Opening stock+(purchases-closing stock)-slaes
Or
(Opening stock+purchases)-(sales+closing stock)