One fifth x+ (one fifth x÷2+50)×6=x

0.2x+0.6x+300=x

300=0.2x

x= 1500

Answer: total length 1500m.

And upstairs, the topic said that it was repaired for another 6 hours, but it was not always repaired for 6 hours.

Landlord, be more accurate when asking questions in the future.