Xiaoqiao brought 216 yuan to buy fruit. If she bought pears, she could buy 18 kilograms; if she bought apples, she could only buy 12 kilograms. How much is an apple more expensive per kilogram than a kilogram of pear?
小巧带了216元去买水果，如果买梨正好可以买18千克；如果买苹果只能买12千克．每千克苹果比每千克梨贵多少元？
<gadget id="calculator">216 / 12</gadget>
<output>18</output>

<gadget id="calculator">216 / 18</gadget>
<output>12</output>

<gadget id="calculator">18 - 12</gadget>
<output>6</output>

<result>6</result>