Li Kuan needs to buy a pair of badminton rackets and several badminton balls. He is running a promotion in two supermarkets, A and B. The plan of A supermarket is to give 10% off all products, and the plan of B supermarket is to buy a pair of rackets and get 3 free For badminton, Li Kuan calculated in his mind. The two supermarkets cost the same amount of money. Given that badminton rackets are 20 yuan per pair and badminton balls are 1 yuan per piece, how many badmintons will Li Kuan plan to buy?
李宽同学需买一副羽毛球拍和若干个羽毛球，正赶上甲、乙两家超市搞促销，甲超市的方案是全部商品一律打九折，乙超市的方案是买一副球拍赠3个羽毛球，李宽在心里算了算，在两家超市花钱一样多，已知羽毛球拍20元/副，羽毛球1元/个，则李宽计划买羽毛球的个数为多少
<gadget id="calculator">18 - 17</gadget>
<output>1</output>

<gadget id="calculator">1 - 0.9</gadget>
<output>0.1</output>

<gadget id="calculator">1 / 0.1</gadget>
<output>10</output>

<result>10</result>