Dumb and Ahgua bought some watermelons, and the weight of the melon that Dumb bought was twice that of Dumb, and Dumb bought nine catties more than Dumb, how many catties of watermelon did they buy together?
阿呆和阿瓜两人买了一些西瓜，阿呆买的瓜的重量是阿瓜的2倍，而且阿呆比阿瓜多买了九斤，他们两人一共买了多少斤西瓜？
<gadget id="calculator">2 - 1</gadget>
<output>1</output>

<gadget id="calculator">9 / 1</gadget>
<output>9</output>

<gadget id="calculator">9 * 2</gadget>
<output>18</output>

<gadget id="calculator">18 + 9</gadget>
<output>27</output>

<result>27</result>