Solve the equation: 6x-20=4x+40.
解方程：6x-20=4x+40．
<gadget id="calculator">20 + 40</gadget>
<output>60</output>

<gadget id="calculator">6 - 4</gadget>
<output>2</output>

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

<result>30</result>