Use 9 nails to form a 3*3 square matrix, and hook rubber bands on the 3 nails to form a triangle. How many triangles can be formed in total?
用9枚钉子组成3*3方阵，用橡皮筋勾在3枚钉子上，组成一个三角形，共可组成多少个三角形．
<gadget id="calculator">7 / 6</gadget>
<output>7/6 = around 1.166667</output>

<gadget id="calculator">9 * 8 * (7/6)</gadget>
<output>84</output>

<gadget id="calculator">84 - 8</gadget>
<output>76</output>

<result>76</result>