Measure an angle, one side of the angle faces the scale "180" on the protractor, and the other side faces the scale "50", what is the angle in degrees?
度量一个角，角的一条边对着量角器上"180"的刻度，另一条边对着刻度"50"，这个角是多少度．
<gadget id="calculator">180 - 50</gadget>
<output>130</output>

<result>130</result>