1, set up a new X application every day, and arrange Y applications for each installation team every day.

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?