The measure of the apex angle of an isosceles triangle is (1/4) of the measure of a base angle. What is the measure of the apex angle of this triangle?
一个等腰三角形顶角的度数是一个底角的度数的(1/4)，这个三角形的顶角是多少度．
<gadget id="calculator">1 + 4 + 4</gadget>
<output>9</output>

<gadget id="calculator">180 / 9</gadget>
<output>20</output>

<result>20</result>