A store increases the cost of a certain garment by 15% and then sells it at 10% off the marked price. As a result, each garment can still make a profit of 7 yuan. What is the cost price of each piece of this garment? (using a linear equation in one variable)
一家商店将某种服装按成本提高15%后标价，又以标价的9折卖出，结果每件服装仍可获利7元，问这种服装每件的成本价是多少元．(用一元一次方程)
<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">(3/20) * (9/10)</gadget>
<output>27/200 = around 0.135</output>

<gadget id="calculator">(27/200) - 1</gadget>
<output>-173/200 = around -0.865</output>

<gadget id="calculator">(9/10) + (-173/200)</gadget>
<output>7/200 = around 0.035</output>

<gadget id="calculator">7 / (7/200)</gadget>
<output>200</output>

<result>200</result>