The whole class of 42 people lined up in a row. Counting from the left, Xiao Hua is the 24th, and counting from the right, Xiao Ming is the 24th. How many people are there between Xiao Hua and Xiao Ming?
全班42人排成一列横队．从左面数起，小华是第24个，从右面数起，小明是第24个，小华和小明之间有多少人．
<gadget id="calculator">24 - 42 - 2</gadget>
<output>-20</output>

<gadget id="calculator">24 + (-20)</gadget>
<output>4</output>

<result>4</result>