A protractor is used to measure an angle. The two sides of the angle coincide with the 20° and 70° scale marks respectively. What is the angle?
量角器量角，角的两边分别与20°和70°刻度线重合，这个角是多少°．
<gadget id="calculator">70 - 20</gadget>
<output>50</output>

<result>50</result>