A rectangular piece of paper, (4/7) is painted red, (2/7) is painted blue, what percentage of the paper is not painted?
一张长方形的纸，(4/7)涂红色，(2/7)涂蓝色，没涂的占这张纸的几分之几？
<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 - (4/7) - (2/7)</gadget>
<output>1/7 = around 0.142857</output>

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