Cash- $21,000
Accounts Receivable - $42,000
Inventory -??
PrePaid Items - $9,000
__________

Long-Term Assets
Building -??
Less: Accumulated depreciation - (39,000)
Total long-term assets - 210,000
________
Total Assets - 342,500

Since this is a bookkeeping question, I'm going to assume that you are just starting to learn about the books and so I'm going to make this a little lesson. Please don't mind if I say something you already know.

The only long-term assets listed are building and accu. Depreciation on the building. On your balance sheet, fixed assets such as buildings are shown as: the original cost of the asset less accumulated depreciation = net cost of the building. If the only L-T asset is the building, you should now be able to figure out the cost of the builing. X - 39,000 = 210,000

Short Term Assets + L-T Assets = Total Assets. You know long-term assets and you know total assets, so you should be able to figure out short term assets. All of the other accounts listed are short term.

If you want to post your answers, I'll let you know if you are doing it right.