It is known that ∠AOB=140°, OC is the angle bisector of ∠AOB, the ray OD is inside ∠AOB, ∠AOD=50°, then what is ∠DOC=.
已知∠AOB=140°，OC是∠AOB的角平分线，射线OD在∠AOB的内部，∠AOD=50°，那么∠DOC=多少．
<gadget id="calculator">140 / 2</gadget>
<output>70</output>

<gadget id="calculator">70 - 50</gadget>
<output>20</output>

<result>20</result>