The sum of the numerator and denominator of a fraction is 30. If you subtract 2 from the numerator and add 7 to the denominator, the new fraction will be 3/2 after division. What is the original fraction?
一个分数的分子和分母的和是30，如果将分子减去2，分母加上7，新的分数约分后是3/2，原来的分数是多少？
<gadget id="calculator">30 - 2</gadget>
<output>28</output>

<gadget id="calculator">28 + 7</gadget>
<output>35</output>

<gadget id="calculator">3 + 2</gadget>
<output>5</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">35 * (3/5)</gadget>
<output>21</output>

<gadget id="calculator">21 + 2</gadget>
<output>23</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">35 * (2/5)</gadget>
<output>14</output>

<gadget id="calculator">14 - 7</gadget>
<output>7</output>

<gadget id="calculator">23 / 7</gadget>
<output>23/7 = around 3.285714</output>

<result>23/7 = around 3.285714</result>