please explain

Practice 3.8 - Record adjustments on 12/31/XI assuming no previous adjustments that year. 1-Jan Purchased $5,500 of supplies. On 12/31 only $200 are left. 1-Feb Purchased a new computer for $3,000. It has an expected life of 3 years and salvage value of $200. 1-Apr Paid $6,000 for 12 months insurance in advance. 1-Aug Received $3,600 advance from a customer (for 6 months work). 1-Oct Borrowed $10,000 and signed an 8% 6 month note. Practice 4.5 - Enter the following transactions into Retail Company's general journal in proper form. 6/1 Retail Co. purchased $4,000 inventory terms 2/10, n30 from Vendor Co. 6/2 Retail Co. sold $6,000 of inventory to Customer Co. 1/10, n45 (it cost Retail $1,000) 6/3 Retail Co. returned $500 inventory to Vendor Company. 6/5 Retail Co. paid Vendor Co. in full (ck #523) 6/7 Customer Co. returned $600 inventory to Retail Co. (the inventory cost Retail $100). 6/15 Payment in full was received from Customer Co