The difference between 2 times a number and (4/5) is (1/2), what is this number?
一个数的2倍与(4/5)的差是(1/2)，这个数是多少？
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(4/5) + (1/2)</gadget>
<output>13/10 = around 1.3</output>

<gadget id="calculator">(13/10) / 2</gadget>
<output>13/20 = around 0.65</output>

<result>13/20 = around 0.65</result>