Final answer:
The effect of transaction 3 on the accounting equation elements is that Assets (Supplies) decrease by $450 and Liabilities (Accounts Payable) increase by $450.
Step-by-step explanation:
The effect of transaction 3 on the accounting equation elements is option A) Assets (Supplies) decrease by $450; Liabilities (Accounts Payable) increase by $450.
Transaction 3 states that the company purchased supplies on account for $450. When this transaction occurs, the company's assets, specifically supplies, will decrease by $450 because they are being used up or consumed. At the same time, the company's liabilities, specifically accounts payable, will increase by $450 because they owe this amount to their supplier for the supplies purchased on credit.