please help me find the percentages for each of these

\begin{tabular}{|c|c|c|} \hline Problem 1 & $ (Dollars) & % (Percentages) \\ \hline Net Sales & $135,000 & \\ \hline Cost of Goods Sold & $120,000 & \\ \hline Gross Margin & $15,000 & \\ \hline Operating Expenses & $11,500 & \\ \hline Profit/Loss & $3,500 & \\ \hline \end{tabular} \begin{tabular}{|c|r|l|} \hline Problem 2 & $ (Dollars) & % (Percentages) \\ \hline Net Sales & $110,000 & \\ \hline Cost of Goods Sold & $80,000 & \\ \hline Gross Margin & $30,000 & \\ \hline Operating & $35,000 & \\ \hline Expenses & ($5,000) & \\ \hline Profit/Loss & & \\ \hline \end{tabular} \begin{tabular}{|c|r|l|} \hline Problem 3 & $ (Dollars) & % (Percentages) \\ \hline Net Sales & $300,000 & \\ \hline Cost of Goods Sold & $180,000 & \\ \hline Gross Margin & $120,000 & \\ \hline Operating Expenses & $90,500 & \\ \hline Profit/Loss & $29,500 & \\ \hline \end{tabular} \begin{tabular}{|c|r|l|} \hline Problem 4 & $ (Dollars) & % (Percentages) \\ \hline Net Sales & $278,000 & \\ \hline Cost of Goods Sold & $190,000 & \\ \hline Gross Margin & $88,000 & \\ \hline Operating & $78,500 & \\ \hline Expenses & $9,500 & \\ \hline Profit/Loss & \\ \hline \end{tabular} \begin{tabular}{|c|r|l|} \hline Problem 5 & $ (Dollars) & % (Percentages) \\ \hline Net Sales & $495,000 & \\ \hline Cost of Goods Sold & $250,000 & \\ \hline Gross Margin & $245,000 & \\ \hline Operating Expenses & $198,568 & \\ \hline Profit/Loss & $46,432 & \\ \hline \end{tabular}