Honghong bought 11 math books, each for 4 yuan, and paid 50 yuan, how much should she get back?
红红买11本数学本，每本4元，付了50元，应找回多少元．
<gadget id="calculator">11 * 4</gadget>
<output>44</output>

<gadget id="calculator">50 - 44</gadget>
<output>6</output>

<result>6</result>