The cafeteria brings 80 tons of coal, and takes 40 tons in 10 days. How many tons are left? What is the correct column
食堂运来80吨煤，10天共用去40吨，还剩多少吨？正确列式是多少
<gadget id="calculator">80 - 40</gadget>
<output>40</output>

<result>40</result>