A pile of coal weighs 720 kilograms, and 80 kilograms remain after burning for four months. How many kilograms of coal are burned on average every month?
一堆煤720千克，烧了四个月后还剩80千克，平均每个月烧煤多少千克？
<gadget id="calculator">720 - 80</gadget>
<output>640</output>

<gadget id="calculator">640 / 4</gadget>
<output>160</output>

<result>160</result>