Li Na used 1,000 yuan to buy 21 cartons of milk and donated them to the disaster area, leaving 55 yuan. How much is each carton of milk?
李娜拿1000元钱买了21箱牛奶捐给灾区，还剩55元，每箱牛奶多少钱？
<gadget id="calculator">1_000 - 55</gadget>
<output>945</output>

<gadget id="calculator">945 / 21</gadget>
<output>45</output>

<result>45</result>