In an isosceles triangle, the ratio of the base angle to the apex angle is 7:4, what is the base angle?
一个等腰三角形，底角与顶角度数的比是7：4，底角是多少度？
<gadget id="calculator">7 + 7 + 4</gadget>
<output>18</output>

<gadget id="calculator">7 / 18</gadget>
<output>7/18 = around 0.388889</output>

<gadget id="calculator">180 * (7/18)</gadget>
<output>70</output>

<result>70</result>