The next day, the remaining 5/8 was repaired, that is, all = (1-7/20) * 5/8 =13/32;

The second day was repaired 1800 meters more than the first day, and the repaired part accounted for =13/32-7/20 = 9/160 of the total length;

So the road length =1800 ÷ 9/160 = 32000m.