Which of the following is not correct equation?

Purchases + opening stock - cost of goods sold = closing stock
Opening stock + purchases - closing stock = cost of goods sold
Closing stock - cost of goods sold - purchases = Opening stock
Cost of goods sold + closing stock - purchases = Opening stock

The correct answer is C. Closing stock – cost of goods sold – purchases = Opening stock.

The equation for cost of goods sold is:

Cost of goods sold = Opening stock + Purchases – Closing stock

Therefore, the equation for opening stock is:

Opening stock = Cost of goods sold + Purchases – Closing stock

The equation for closing stock is:

Closing stock = Cost of goods sold + Purchases – Opening stock

Therefore, the equation C. Closing stock – cost of goods sold – purchases = Opening stock is not correct.