1. 20, 40, 60, ... , 500, 520
2. 80, 100, ..., 1000
3. 32, 40, ..., 72, 80
4. a) 2, 4, 6, ..., 122, 124
b) 3, 6, 9, ..., 120, 123
c) 6, 12, ..., 114, 120
d) combine the list of numbers in a) and b)
5. 102, 104, ..., 998, 1000
b) 108, 117, ..., 999
c) 108, 126, ..., 990
d) combine the list of numbers in a) and b)