Personal income adjustment tax is one of the taxes levied by the state. It is exempted below 1,000 yuan, and the excess is calculated and taxed in stages. 5% tax is levied on the part of 1000 yuan to 1500 yuan; 10% tax is levied on the part of 1500 yuan to 2000 yuan; 15% tax is levied on the part of 2000 yuan to 3000 yuan. According to the monthly income of an employee, the tax payable is 90 yuan. How much is the employee's monthly income?
个人收人调节税是国家征税的税种之一，1000元以下免税，超出部分分段计算征税．1000元以上至1500元的部分，征收5%的税；1500元以上至2000元的部分，征收10%的税；2000元以上至3000元的部分，征收15%的税．某职员根据月收入，应纳税90元，这位职员月收人多少元？
<gadget id="calculator">2_000 - 1_500</gadget>
<output>500</output>

<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">500 * (1/10)</gadget>
<output>50</output>

<gadget id="calculator">1_500 - 1_000</gadget>
<output>500</output>

<gadget id="calculator">5 / 100</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">500 * (1/20)</gadget>
<output>25</output>

<gadget id="calculator">50 + 25</gadget>
<output>75</output>

<gadget id="calculator">90 - 75</gadget>
<output>15</output>

<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">15 / (3/20)</gadget>
<output>100</output>

<gadget id="calculator">2_000 + 100</gadget>
<output>2_100</output>

<result>2_100</result>