The perimeter of an isosceles triangle is 70 cm, and the ratio of one side to the base is 2:3. What is the base of this isosceles triangle?
一个等腰三角形的周长是70厘米，一条腰与底的比是2：3，这个等腰三角形的底是多少？
<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>