If the mother's monthly income exceeds 3,500 yuan, she should pay personal income tax at a rate of 5%. The mother pays 30 yuan of personal income tax. What is the actual monthly income of the mother?
妈妈月收入超过3500元的部分，应按5%的税率交纳个人所得税，妈妈缴纳个人所得税30元，妈妈月实际收入是多少元．
<gadget id="calculator">5 / 100</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">30 / (1/20)</gadget>
<output>600</output>

<gadget id="calculator">600 + 3_500</gadget>
<output>4_100</output>

<result>4_100</result>