eBay/StockX (third party) Platform Fees

I have a full-time job but also do some selling through eBay and StockX to the point where combined sales total above $20,000 but profit is around $2,000-$3,000. Since I have to report this as a "business" since it won't be considered a hobby can I deduct platform fees from my profits?

 

Ex: StockX Fees

Sold an item for $208 but StockX deducted a Transaction Fee (9%), Payment Processing Fee (3%) and a shipping cost of $4 for them to give me a shipping label. The amount they sent me through PayPal was $179.04. Of those fees what can I claim as a deduction? Can I claim all those fees as deductions since they are fees that I need to pay to sell my item?

Also, if I purchased a new laptop to print out shipping labels, handle selling, and anything related with selling can I also claim that cost?