The sum of a number and (13/20), and then subtract (3/5), the difference is (1/10), find this number.
一个数与(13/20)的和，再减去(3/5)，差是(1/10)，求这个数．
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">13 / 20</gadget>
<output>13/20 = around 0.65</output>

<gadget id="calculator">(3/5) - (13/20)</gadget>
<output>-1/20 = around -0.05</output>

<gadget id="calculator">(1/10) + (-1/20)</gadget>
<output>1/20 = around 0.05</output>

<result>1/20 = around 0.05</result>