修一条公路,已经修了21千米,还剩下15千米,一共修多少千米?;{'T1d1p4L4h
算式:提示;g-f3b*d1@;q+d.z4M;^;{'T1d1p4L4h
答:一共修.n;O5W'm/q千米。;{'T1d1p4L4h