(2/5) of a number is less than (3/4) (1/2), find this number. (solution by equation)
一个数的(2/5)比(3/4)少(1/2)，求这个数．(用方程解)
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

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

<gadget id="calculator">(3/4) - (1/2)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(1/4) / (2/5)</gadget>
<output>5/8 = around 0.625</output>

<result>5/8 = around 0.625</result>