In a triangle, there are two angles of 72° and 27° respectively, so how many degrees must the other angle of this triangle be.
在一个三角形中，有两个角分别是72°和27°，那么这个三角形的另外一个角一定是多少度．
<gadget id="calculator">72 + 27</gadget>
<output>99</output>

<gadget id="calculator">180 - 99</gadget>
<output>81</output>

<result>81</result>