((1/2)-(1/3))+((1/3)-(1/4))+((1/4)-(1/5))+…+((1/19) -(1/20))
((1/2)-(1/3))+((1/3)-(1/4))+((1/4)-(1/5))+…+((1/19)-(1/20))
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/2) - (1/20)</gadget>
<output>9/20 = around 0.45</output>

<result>9/20 = around 0.45</result>