Xiaoming puts 3 pineapples and 5 apples on the left end of the balance, and puts 1 pineapple and 9 apples on the right end of the balance. The balance is just balanced, and you know how many apples a pineapple is equal to.
小明在天平的左端放了3个菠萝5个苹果，在天平的右端放入1个菠萝9个苹果，天平正好平衡，你知道一个菠萝等于多少个苹果．
<gadget id="calculator">9 - 5</gadget>
<output>4</output>

<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<result>2</result>