Solve the equation: 2*(x-1-1)=x.
解方程：2*(x-1-1)=x．
<gadget id="calculator">2 + 2</gadget>
<output>4</output>

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

<gadget id="calculator">4 / 1</gadget>
<output>4</output>

<result>4</result>