A fraction after division is (3/4). If the numerator of this fraction is subtracted by 21, and the denominator is subtracted by 30, a new fraction (4/5) can be obtained after division. Then the original fraction before division is How many.
一个分数约分后是(3/4)，如果这个分数的分子减去21，分母减去30，约分后就可以得到一个新的分数(4/5)，那么原来的分数约分前是多少．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(4/5) * 30</gadget>
<output>24</output>

<gadget id="calculator">24 - 21</gadget>
<output>3</output>

<gadget id="calculator">(4/5) * 4</gadget>
<output>16/5 = around 3.2</output>

<gadget id="calculator">(16/5) - 3</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">3 / (1/5)</gadget>
<output>15</output>

<gadget id="calculator">3 * 15</gadget>
<output>45</output>

<gadget id="calculator">4 * 15</gadget>
<output>60</output>

<gadget id="calculator">45 / 60</gadget>
<output>3/4 = around 0.75</output>

<result>3/4 = around 0.75</result>