The fruit shop brings four kinds of fruits. Apples and pears account for (1/2) of the total, apples and watermelons account for (2/5) of the total, and apples and bananas account for (1/4) of the total. So how many apples account for the total.
水果店运来四种水果，苹果和梨共占总数的(1/2)，苹果和西瓜共占总数的(2/5)，苹果和香蕉共占总数的(1/4)．那么苹果占总数的多少．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

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

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/2) + (2/5) + (1/4)</gadget>
<output>23/20 = around 1.15</output>

<gadget id="calculator">(23/20) - 1</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">(3/20) / 2</gadget>
<output>3/40 = around 0.075</output>

<result>3/40 = around 0.075</result>