A piece of land used to grow two kinds of vegetables, radish and potato, and the planting area of radish accounted for 3/10 of the total area of the land. Now, according to the needs of the market, the planting area of the two vegetables should be adjusted to the same size. Then, the number of potatoes should be changed. Plant radishes.
一块地原来种萝卜、土豆两种蔬菜，萝卜种植面积占该地总面积的(3/10)，现在根据市场需要，要把两种蔬菜种植面积调整为同样大小，那么，土豆的多少应该改种萝卜．
<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(7/10) - (1/2)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/5) / (7/10)</gadget>
<output>2/7 = around 0.285714</output>

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