Dandan has 15 yuan, and Fang Fang has 12.5 yuan. They are going to buy a box of color pens together, and there is still a difference of 1.2 yuan. How much is this box of color pens?
丹丹有15元钱，方方有12.5元钱，两个人准备合买一盒彩笔，还差1.2元，这盒彩笔多少钱？
<gadget id="calculator">15 + 12.5</gadget>
<output>27.5</output>

<gadget id="calculator">27.5 + 1.2</gadget>
<output>28.7</output>

<result>28.7</result>