Uncle Zhang received a supplementary salary of 240 yuan. There are 50 pieces of RMB in three denominations of 2 yuan, 5 yuan, and 10 yuan. Among them, there are as many pieces of 2 yuan and 5 yuan.
张叔叔领得补发工资240元，有2元、5元、10元三种面值的人民币共50张，其中2元和5元的张数一样多，那么10元的有多少张．
<gadget id="calculator">260 / 13</gadget>
<output>20</output>

<gadget id="calculator">2 * 20</gadget>
<output>40</output>

<gadget id="calculator">50 - 40</gadget>
<output>10</output>

<result>10</result>