The school bought back 20 boxes of chalk, 24 boxes in each box. After 158 boxes are used up, how many boxes are left?
学校买回20箱粉笔，每箱24盒，用去158盒后，还剩多少盒？
<gadget id="calculator">24 * 20</gadget>
<output>480</output>

<gadget id="calculator">480 - 158</gadget>
<output>322</output>

<result>322</result>