Final answer:
The quantity equation of money is MV = PQ. Nick needs to add an amount of money to the card represented by m. The equation (money on card now) + (money Nick adds) = (final amount on card) + m represents the situation.
Step-by-step explanation:
The quantity equation of money is MV = PQ, where M represents the amount of money, V represents the velocity of money, P represents the price level, and Q represents the quantity of goods and services. In this case, we are given that initially, V = 3, M = 4,000 billion, and P = 100. To complete the equation, we need to determine the final amount on the card and add the amount Nick should add, represented by m. Therefore, the equation becomes (money on card now) + (money Nick adds) = (final amount on card) + m.