In 2005, 4,200 households in Linshan Village had landline telephones, an increase of 20% over last year. How many households had telephones last year?
2005年邻山村有4200户家庭拥有电话座机，比去年增加了20%，去年有多少户家庭拥有电话？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">4_200 / (6/5)</gadget>
<output>3_500</output>

<result>3_500</result>