It takes (3/4) hours to produce a part, which is shortened by (1/2) hours compared to the original one. How much is it shortened?
在生产一种零件，现在需要(3/4)小时，比原来缩短了(1/2)小时，缩短了多少
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(3/4) + (1/2)</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">(1/2) / (5/4)</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>