When using a spring scale to weigh 3kg of cucumbers, the length of the spring is 12.75cm; when weighing 5kg of tomatoes, the length of the spring is 13.25cm. How many centimeters is the length of the spring when there is no object?
用弹簧秤称3kg黄瓜时，弹簧长12.75cm；称5kg西红柿时，弹簧长13.25厘米．在没有物体时，弹簧长多少厘米？
<gadget id="calculator">13.25 - 12.75</gadget>
<output>0.5</output>

<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">0.5 / 2</gadget>
<output>0.25</output>

<gadget id="calculator">0.25 * 3</gadget>
<output>0.75</output>

<gadget id="calculator">12.75 - 0.75</gadget>
<output>12</output>

<result>12</result>