In an isosceles triangle, the ratio of the base angle to the top angle is 3:4, what is the measure of the top angle of this triangle?
一个等腰三角形，一个底角度数和顶角的比是3：4，这个三角形顶角的度数是多少．
<gadget id="calculator">3 + 3 + 4</gadget>
<output>10</output>

<gadget id="calculator">4 / 10</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">180 * (2/5)</gadget>
<output>72</output>

<result>72</result>