The shape of a vegetable field is an isosceles triangle, the circumference is 21m, and the waist length of one is the base length (2/3), how many meters is the base length?
一块菜地的形状是等腰三角形，周长是21m，一条腰长是底长的(2/3)，底长为多少米？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 + (2/3) + (2/3)</gadget>
<output>7/3 = around 2.333333</output>

<gadget id="calculator">21 / (7/3)</gadget>
<output>9</output>

<result>9</result>