In the known triangle ABC, ∠C=80°, ∠A-∠B=40°, find the degree of ∠B.
已知三角形ABC中，∠C=80°，∠A-∠B=40°，求∠B的度数．
<gadget id="calculator">180 - 40 - 80</gadget>
<output>60</output>

<gadget id="calculator">1 + 1</gadget>
<output>2</output>

<gadget id="calculator">60 / 2</gadget>
<output>30</output>

<result>30</result>