Xingsheng Food Factory produced 3,960 tons of chocolate last year. This year it produced 79 tons more than last year, and the year before last was 186 tons less than this year. How many tons of chocolate did it produce in the year before last?
兴盛食品厂去年生产巧克力3960吨，今年比去年多生产79吨，前年比今年生少186吨，求前年生产巧克力多少吨？
<gadget id="calculator">79 - 186</gadget>
<output>-107</output>

<gadget id="calculator">3_960 + (-107)</gadget>
<output>3_853</output>

<result>3_853</result>