The total weight of the three watermelons is 23 kg, the total weight of the first and second watermelons is 12 kg, the total weight of the second and third watermelons is 17 kg, how much does the weight of the second watermelon weigh?
三个西瓜共重23千克，第一、二个西瓜共重12千克，第二、三个西瓜共重17千克，第二个西瓜重多少千克？
<gadget id="calculator">17 - 23</gadget>
<output>-6</output>

<gadget id="calculator">12 + (-6)</gadget>
<output>6</output>

<result>6</result>