Sales Ledger account

1. control account = Cash at bank, Account receivable and Account payable nomrally

2. We sold goods on credit to A for $2000:

A/C Pay. 2,000 Dr ; goods 2,000 Cr

We purchased good credit from A for $8000:

goods 8,000 Dr : A/C Rec. 8,000 Cr

NB: If the question ask you write down adjusted entry, then you have to adjust A/C Pay. and A/C Rec.

3. Do you a T account???

200 Dr = someone else owed you $$ on 1/1 (actually, I think 200 is open balance)
300 Dr = someone else owed you $$ on 6/1 from sales (goods)

Therefore, the closing balance should be 500 Dr because A/C Pay. is Dr side rather than credit side.