An isosceles triangle is formed with a 70 cm long iron wire. The ratio of the length of one waist of the triangle to the length of the base is 2:3. What is the length of the base of this triangle in cm?
用70厘米长的铁丝围成一个等腰三角形，三角形一条腰与底边长度的比是2：3，这个三角形的底边长是多少厘米？
<gadget id="calculator">2 + 2 + 3</gadget>
<output>7</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">70 * (3/7)</gadget>
<output>30</output>

<result>30</result>