The charge for developing photos in the photo studio is as follows: 2 yuan for printing, and 0.45 yuan for an additional photo. Mr. Li spent a total of 15.5 yuan developing the photos. How many photos did he add? (Please list the equation solution)
照相馆冲洗照片是这样收费的：冲卷费2元，加洗一张照片0.45元．李老师冲洗照片共花了15.5元．他加洗了多少张照片？(请列方程解答)
<gadget id="calculator">15.5 - 2</gadget>
<output>13.5</output>

<gadget id="calculator">13.5 / 0.45</gadget>
<output>30</output>

<result>30</result>