The mall shipped 500 boxes of children's building blocks, and after 3 months of selling, there are still 116 boxes left. How many boxes of building blocks are sold per month on average?
商场运进500盒儿童积木，卖了3个月后还剩116盒，平均每月卖多少盒积木？
<gadget id="calculator">500 - 116</gadget>
<output>384</output>

<gadget id="calculator">384 / 3</gadget>
<output>128</output>

<result>128</result>