There are 9 boxes of oranges in the fruit shop with the same weight. If 20 kilograms are taken out of each box, the remaining oranges in the 9 boxes are exactly equal to the weight of the original 4 boxes. How much does each box of oranges weigh?
水果店有9箱一样重的橙子，如果从每个箱子里取出20千克，9箱里剩下的橙子正好等于原来4箱的重量，原来每箱橙子重多少千克？
<gadget id="calculator">20 * 9</gadget>
<output>180</output>

<gadget id="calculator">9 - 4</gadget>
<output>5</output>

<gadget id="calculator">180 / 5</gadget>
<output>36</output>

<result>36</result>