There are three boxes containing black and white chess pieces, and the total number of chess pieces in the three boxes is equal. It is known that there are as many white pieces in the first box as there are black pieces in the second box, and the number of white pieces in the third box is (2/5) of the total number of all white pieces, then all the black pieces in these three boxes account for all the pieces the total number
有三个盒子分别在里面装着黑白两种颜色的棋子，并且三个盒子的棋子总数相等．已知第一个盒里的白子与第二个盒里的黑子同样多，第三个盒里的白子是所有白子总数的(2/5)，则这三个盒子里的所有黑子占全部棋子总数的多少
<gadget id="calculator">5 - 2</gadget>
<output>3</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 - (2/3)</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 + (1/3)</gadget>
<output>4/3 = around 1.333333</output>

<gadget id="calculator">1 + 1 + 1</gadget>
<output>3</output>

<gadget id="calculator">(4/3) / 3</gadget>
<output>4/9 = around 0.444444</output>

<result>4/9 = around 0.444444</result>