The measure of a base angle of an isosceles triangle is 25% of the apex angle. What is the measure of a base angle of an isosceles triangle?
等腰三角形的一个底角的度数是顶角的25%，它的一个底角是多少度．
<gadget id="calculator">180 / 1.5</gadget>
<output>120</output>

<gadget id="calculator">120 * 0.25</gadget>
<output>30</output>

<result>30</result>