Mr. Li bought 15 copies of "Science and Technology Expo" at 3.00 yuan each, and several copies of "Character Stickers" at 2.50 yuan each. He spent 100 yuan and got 30 yuan back. How many copies of "Word Stickers" did you buy in total?
李老师买了15本《科技博览》，每本3.00元，又买了若干本每本2.50元的《字贴》，支出100元，找回30元．一共买了多少本《字贴》？
<gadget id="calculator">3 * 15</gadget>
<output>45</output>

<gadget id="calculator">100 - 30 - 45</gadget>
<output>25</output>

<gadget id="calculator">25 / 2.5</gadget>
<output>10</output>

<result>10</result>