(1)8400*8/10=6720元(2)(8400-6720)/6720*100%=25%
(1)8400*0.8=6720(2)(8400/6720-1)*100%=25%
(1)8400*0.8=6720元
1。。8400*0.82。。0.2*8400/0.8*8400
(1)8400*80/100=6720(2)(8400-6720)/6720=0.25=百分之25