There are 8 points in a plane, any 3 of which are not on the same straight line. After drawing a straight line every two points, how many straight lines can be drawn at most?
一个平面内有8个点，其中任意3个点都不在同一条直线上．经过每两点画一条直线，最多可以画多少条直线？
<gadget id="calculator">8 - 1</gadget>
<output>7</output>

<gadget id="calculator">7 * 8</gadget>
<output>56</output>

<gadget id="calculator">56 / 2</gadget>
<output>28</output>

<result>28</result>