简算方法如下:39×82+19×39-19=39×82+19×39-(39-20)=39×82+19×39-39+20=39×(82+19-1)+20=39×100+20=3920
39×82+19×39-19=39×82+19×39-(39-20)=39×82+19×39-39+20=39×(82+19-1)+20=39×100+20=3920