In physical education class, when Xiao Hua stood in a team, he was the 9th from the front to the back, and the 12th from the back to the front, and asked how many people there were in this team.
小华上体育课，站队时，从前向后数他是第9个，从后向前数他是第12个，问这队共有多少人．
<gadget id="calculator">12 - 1</gadget>
<output>11</output>

<gadget id="calculator">9 + 11</gadget>
<output>20</output>

<result>20</result>