There are 520 kilograms of apples, bananas and pears in the fruit shop. It is known that the mass of apples is 3 times that of pears, and the mass of bananas is 3 times that of apples. How many kilograms of pears are there in the fruit shop?
水果店里有苹果、香蕉和梨子一共520千克，已知苹果的质量是梨子质量的3倍，香蕉的质量是苹果质量的3倍．水果店里有梨子多少千克？
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">9 + 3 + 1</gadget>
<output>13</output>

<gadget id="calculator">520 / 13</gadget>
<output>40</output>

<result>40</result>