X+60x = 3 * 60y600+20x = 5 * 20y = 20y =10 of 600.
There are 20 users who apply for refitting electric meters every day.
2, set n.
5* 10n=600+5*20,n= 14。
The power supply company needs to arrange at least 14 refitting teams to install at the same time?