The mass of the watermelon in the fruit store is 100 kg more than that of the apple, and after the watermelon is sold (1/3), the mass of the apple is 20 kg more than that of the watermelon. How many kilograms of watermelon are there in the fruit store?
水果店里西瓜的质量比苹果多100千克，西瓜卖出(1/3)后苹果的质量又比西瓜多了20千克，水果店原来有西瓜多少千克？
<gadget id="calculator">100 + 20</gadget>
<output>120</output>

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

<gadget id="calculator">120 / (1/3)</gadget>
<output>360</output>

<result>360</result>