Mom deposits a sum of money in the bank for 3 years on a regular basis with an annual interest rate of 4.85%. When the maturity expires, she will get a total of 9105.8 yuan in principal and after-tax interest (interest tax rate is 5%). How much money does mom start depositing in the bank?
妈妈把一笔钱存入银行，定期3年，年利率为4.85%，到期时她获得本金和税后利息共9105.8元(利息税率为5%)，妈妈开始存入银行多少钱？
<gadget id="calculator">4.85 / 100</gadget>
<output>0.0485</output>

<gadget id="calculator">0.0485 * 3</gadget>
<output>0.1455</output>

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

<gadget id="calculator">0.0485 * 3 * (1/20)</gadget>
<output>0.007275</output>

<gadget id="calculator">0.1455 - 0.007275</gadget>
<output>0.138225</output>

<gadget id="calculator">1 + 0.138225</gadget>
<output>1.138225</output>

<gadget id="calculator">9_105.8 / 1.138225</gadget>
<output>8_000</output>

<result>8_000</result>