your sister can get $30 per day for selling clothes at the market. but she has to $60 at first for renting a stand. you can get $20 per day for helping neighbor rake lawns.after how many days will your sister earn as much as you?

Day Sis you
1 -30 20
2 0 40
3 30 60
4 60 80
5 90 100
6 120 120

So day 6.