Answer:
Following would be the journal entry for purchase of office supplies;
Office Supplies A/C Dr. $2500
To Cash A/C $800
To Accounts Payables A/C $1700
(Being office supplies purchased partly for cash, partly on credit, being recorded)
Purchases is a nominal account so the rule which applies is, debit all expenses and credit all incomes and gains.
Cash is also a real account so the principle which applies is, debit what comes in and credit what goes out.
Accounts Payable is also a real account so the same principle applies, as for cash.