When a "little sloppy" measures an angle with a protractor, he mistakenly regards the scale on the outer circle as the scale on the inner circle and reads 150°. What is the correct degree?
"小马虎"用量角器测量一个角时，由于误把外圈刻度当成内圈刻度而读得度数为150°，正确的度数应该是多少°
<gadget id="calculator">180 - 150</gadget>
<output>30</output>

<result>30</result>