The perimeter of an isosceles triangle is 30 cm and the base is 3 cm longer than the waist. What is its base in centimeters?
一个等腰三角形的周长是30厘米，底比腰长3厘米．它的底是多少厘米？
<gadget id="calculator">30 - 3</gadget>
<output>27</output>

<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<gadget id="calculator">27 / 3</gadget>
<output>9</output>

<gadget id="calculator">9 + 3</gadget>
<output>12</output>

<result>12</result>