A and B have a total of 40 balls. A has 2 more balls than B. How many balls does B have?
甲和乙共有40个球，甲比乙的球多2个，乙有多少个球．
<gadget id="calculator">40 - 2</gadget>
<output>38</output>

<gadget id="calculator">38 / 2</gadget>
<output>19</output>

<result>19</result>