The ratio of number A to number B is 5:3. If number A increases by 20 and number B decreases by 4, the ratio is 3. What is the original number of A?
甲数与乙数的比是5：3，如果甲数增加20，乙数减少4，比值是3，甲数原来是多少．
<gadget id="calculator">4 * 3</gadget>
<output>12</output>

<gadget id="calculator">20 + 12</gadget>
<output>32</output>

<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">9 - 5</gadget>
<output>4</output>

<gadget id="calculator">32 / 4</gadget>
<output>8</output>

<gadget id="calculator">8 * 5</gadget>
<output>40</output>

<result>40</result>