In a triangular flower field, Chinese roses are planted on its three sides, and one tree is planted at each vertex. If 8 trees are planted on each side, how many roses are planted in total?
一个三角形花地，在它的三条边上都种上月季花，并且每一个顶点种一棵，如果每边种8棵，一共种多少棵月季花．
<gadget id="calculator">8 * 3</gadget>
<output>24</output>

<gadget id="calculator">24 - 3</gadget>
<output>21</output>

<result>21</result>