Xiao Ming gave away 15 of his own stamps and then collected 20. At this time, he has 49 stamps. How many stamps did Xiao Ming originally have?
小明把自己的邮票送掉15张后又收集了20张，这时他有49张邮票，小明原来有邮票的张数是多少张
<gadget id="calculator">49 - 20</gadget>
<output>29</output>

<gadget id="calculator">29 + 15</gadget>
<output>44</output>

<result>44</result>