If the numerator of a simplest fraction is doubled and the denominator is reduced by three times, it is equal to (4/7). What is the simplest fraction?
把一个最简分数的分子扩大2倍，分母缩小3倍后等于(4/7)，这个最简分数是多少．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">7 * 3</gadget>
<output>21</output>

<gadget id="calculator">2 / 21</gadget>
<output>2/21 = around 0.095238</output>

<result>2/21 = around 0.095238</result>