There are two kinds of operations: "﹟" and "△", and the operation method is: a﹟b=2a+b, a△b=2a-b, when the above-mentioned operations are mixed elements, they must be performed from left to right , calculate first in the brackets, what is the value of (2/3)﹟(5△(4/5))△((3﹟(5/7))△7).
现有两种运算："﹟"和"△"，其运算法则是：a﹟b=2a+b，a△b=2a-b，上面规定的运算作混合元算时，必须从左到右，括号内先算，则(2/3)﹟(5△(4/5))△((3﹟(5/7))△7)的值为多少．
<gadget id="calculator">175 / 21</gadget>
<output>25/3 = around 8.333333</output>

<result>25/3 = around 8.333333</result>