求时间的那题我算出来跟2楼一样,下一题:(1)设原售电价为X算式:40(X=0.03)=60(X-0.25)=42.73X=0.5653平段电价为0.5653+0.03谷段为0.5653-0.25(2)0.5653*100-42.73=13.8(元)我算出来是这样的....