The measure of a base angle of an isosceles triangle is (2/5) of its vertex angle. What is the measure of its vertex angle?
一个等腰三角形一个底角的度数是它的顶角的(2/5)，它的顶角度数是多少度．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) + (2/5) + 1</gadget>
<output>9/5 = around 1.8</output>

<gadget id="calculator">180 / (9/5)</gadget>
<output>100</output>

<result>100</result>