Luxia Village expanded the scale of pig breeding. This year, 2,400 pigs were raised, an increase (3/7) from last year. How many pigs were raised last year?
卢下村扩大生猪养殖规模，今年养殖生猪2400头，比去年增加(3/7)，去年养殖生猪多少头？
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">1 + (3/7)</gadget>
<output>10/7 = around 1.428571</output>

<gadget id="calculator">2_400 / (10/7)</gadget>
<output>1_680</output>

<result>1_680</result>