Liu, Guan, and Zhang "Taoyuan three sworn brothers", Zhang Fei prepared 32 catties of sauced beef. Zhang Fei eats the most, eating 4 catties more than Guan Yu and Liu Bei combined. It is known that Zhang Fei ate three times as much as Liu Bei, so how many catties of beef did Guan Yu eat?
刘、关、张"桃园三结义"，张飞准备了32斤酱牛肉．张飞食量最大，吃的比关羽和刘备加起来还多4斤．已知张飞吃的是刘备的3倍，那么关羽吃了多少斤牛肉．
<gadget id="calculator">32 + 4</gadget>
<output>36</output>

<gadget id="calculator">36 / 2</gadget>
<output>18</output>

<gadget id="calculator">18 / 3</gadget>
<output>6</output>

<gadget id="calculator">32 - 18 - 6</gadget>
<output>8</output>

<result>8</result>