A certain brand of woolen sweaters in Wanlong Supermarket, if sold at a 30% discount, will lose 8 yuan, and if sold at a 20% discount, it will earn 10 yuan. What is the purchase price of this brand of woolen sweaters?
万隆超市的某种品牌羊毛衫，若优惠30%销售则赔8元，若优惠20%销售则赚10元，这种品牌羊毛衫的进价是多少元？
<gadget id="calculator">8 + 10</gadget>
<output>18</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">1 - (1/5) - (7/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">18 / (1/10)</gadget>
<output>180</output>

<result>180</result>