Answer: the number's I used were 30, 20, 40
1. 2n-1=39 = 2(20)-1=39 = 40-1=39
2. 2n-60=20 = 2(40)-60=20 = 80-60=20
3. 2n-20=40 = 2(30)-10=40 = 60-20=40
