The number A is the sum of the numbers A and B (3/10), how much less is the number A than the number B.
甲数是甲、乙两数和的(3/10)，甲数比乙数少多少．
<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">(7/10) - (3/10)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) / (7/10)</gadget>
<output>4/7 = around 0.571429</output>

<result>4/7 = around 0.571429</result>