A rectangular piece of paper, (1/7) is painted red, (4/7) is painted blue, what percentage of the paper is not colored?
一张长方形的纸，(1/7)涂红色，(4/7)涂蓝色，没涂色的占这张纸的几分之几？
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">1 - (1/7) - (4/7)</gadget>
<output>2/7 = around 0.285714</output>

<result>2/7 = around 0.285714</result>