Solve the equation: x-(1/10)x-(2/5)=(2/5).
解方程：x-(1/10)x-(2/5)=(2/5)．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) + (2/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">(4/5) / (9/10)</gadget>
<output>8/9 = around 0.888889</output>

<result>8/9 = around 0.888889</result>