If it is stipulated that "↑(a, b)" means the sum of two numbers divided by the difference between these two numbers, for example: ↑(4, 2)=((4+2)/(4-2))=3 , the symbol "↓(a, b)" means the difference between two numbers divided by the sum of these two numbers, for example: (4, 2)=((4-2)/(4+2))=(1/ 3), then: ((↓(↑(8,4), 2))/(↑(2↓(8,4))))=how much.
如果规定符合"↑(a，b)"表示两个数的和除以这两个数的差，例如：↑(4，2)=((4+2)/(4-2))=3，符号"↓(a，b)"表示两个数的差除以这两个数的和，例如：(4，2)=((4-2)/(4+2))=(1/3)，那么：((↓(↑(8，4)，2))/(↑(2↓(8，4))))=多少．
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<result>1/7 = around 0.142857</result>