A triangular vegetable field has a side length ratio of 3:4:5 and a circumference of 84 meters. What is the length of the shortest side in meters?
一块三角形菜地，边长的比是3：4：5，周长为84米，其中最短的边长多少米．
<gadget id="calculator">3 + 4 + 5</gadget>
<output>12</output>

<gadget id="calculator">3 / 12</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">84 * (1/4)</gadget>
<output>21</output>

<result>21</result>