A bag of rice is 50 kilograms, 20 kilograms are used for the first time, and the rest (2/3) is used for the second time, how many kilograms are used for the second time.
一袋大米50千克，第一次用去20千克，第二次用去剩下的(2/3)，第二次用去多少千克．
<gadget id="calculator">50 - 20</gadget>
<output>30</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">30 * (2/3)</gadget>
<output>20</output>

<result>20</result>