Solve the equation: x-(4/5)x=(7/10).
解方程：x-(4/5)x=(7/10)．
<gadget id="calculator">7 / 10</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(7/10) / (1/5)</gadget>
<output>7/2 = around 3.5</output>

<result>7/2 = around 3.5</result>