Green vegetables are 3 yuan per kilogram, and radishes are 4 yuan per kilogram. Aunt Mei brought 20 yuan and left 2 yuan for the bus. If you buy 2 kilograms of green vegetables, how many kilograms of radishes can you buy?
青菜每千克3元，萝卜每千克4元．梅阿姨带了20元钱，乘公交车要留下2元．如果买2千克青菜后，还能买多少千克萝卜．
<gadget id="calculator">20 - 2</gadget>
<output>18</output>

<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">18 - 6</gadget>
<output>12</output>

<gadget id="calculator">12 / 4</gadget>
<output>3</output>

<result>3</result>