Answer:
1) 111, 112
2) 12, 9
3) -12
4) 31, 32, 33
Explanation:
1) n + (n+1) = 223
2n + 1 = 223
2n=222
n = 111 numbers: 111, 112
2) n + (n-3) = 21
2n - 3 = 21
2n=24
n=12 numbers: 12, 9
3) 2*(n+5) = n-2
2n + 10 = n - 2
n = -12 number: -12
4) n + (n+1) + (n+2) = 96
3n + 3 = 96
3n = 93
n=31 numbers: 31, 32, 33