Uncle Wang's orchard harvested 4.2 tons of apples this year, an increase of (1/5) compared to last year. How many tons of apples did Uncle Wang's family harvest last year?
王大叔家的果园今年共收获苹果4.2吨，比去年增加了(1/5)．王大叔家去年收获苹果多少吨？
<gadget id="calculator">1 / 5</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">4.2 / (6/5)</gadget>
<output>3.5</output>

<result>3.5</result>