pears can be exchanged for 2 apples, 9 apples can be exchanged for 3 pineapples, and 6 pineapples can be exchanged for how many pears.
4个梨可换2个苹果，9个苹果可换3个菠萝，6个菠萝可换多少个梨．
<gadget id="calculator">9 / 3</gadget>
<output>3</output>

<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">3 * 3 * 4</gadget>
<output>36</output>

<result>36</result>