Xiao Ming brought 20 yuan, bought a box of colored pens, and left 7.45 yuan, how much is a box of colored pens?
小明带了20元，买了一盒彩笔，还剩7.45元，一盒彩笔多少元？
<gadget id="calculator">20 - 7.45</gadget>
<output>12.55</output>

<result>12.55</result>