3 small sticks are used to place a triangle, 5 sticks are used to place two triangles, 7 sticks are used to place 3 triangles, and how many sticks are used to place 10 sticks?
摆一个三角形用3根小棒，两个三角形用5根，3个用7根，摆10个用多少根？
<gadget id="calculator">2 * 10</gadget>
<output>20</output>

<gadget id="calculator">20 + 1</gadget>
<output>21</output>

<result>21</result>