Uncle Zhang sells a cart of watermelons. After selling (2/3), there are still 30 watermelons left. How many watermelons are there in total?
张叔叔卖一车西瓜瓜，卖了(2/3)后，还剩30个，原来一共有多少个西瓜？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 - (2/3)</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">30 / (1/3)</gadget>
<output>90</output>

<result>90</result>