Sales
Cost of goods sold $ 575,000
Gross profit $1,600,00
General and administrative expense $ 200,000
Selling and marketing expense
Depreciation $ 50,000
Operating income
Interest $ 100,000
Income before taxes
Income taxes (30%)

Simply work your problem backwards, which means you need to solve for sales. Since you know what your gross profit is and what your cost of goods sold is you simply add your cost of goods sold to your Gross profit to get your sales.

Sales - Cost of Goods Sold = Gross profit

So rewritten looks like this:
Sales = Gross Profit + Cost of Goods Sold.