Hongcheng Supermarket brings in 20 kilograms of apples, the weight of oranges is 9/10 that of apples, and the weight of grapes is less than that of oranges (1/3). How much does the weight of grapes weigh in kilograms?
宏城超市运进20千克苹果，桔子的重量是苹果的(9/10)，葡萄的重量比桔子少(1/3)，葡萄重多少千克．
<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">20 * (9/10)</gadget>
<output>18</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/3)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">18 * (2/3)</gadget>
<output>12</output>

<result>12</result>