The store shipped back a total of 720 bottles of orange juice and green tea. 24 bottles/box of orange juice, 24 bottles/box of green tea. Among them, there are 12 boxes of orange juice, how many boxes of green tea are shipped back?
商店运回橘子汁和绿茶共720瓶．橘子汁24瓶/箱，绿茶24瓶/箱．其中橘子汁12箱，运回绿茶多少箱？
<gadget id="calculator">720 / 24</gadget>
<output>30</output>

<gadget id="calculator">30 - 12</gadget>
<output>18</output>

<result>18</result>