Question

D = { x ∈ ℕ | x = 7.k + 1,k ∈ ℕ k ≤ 7 }

Answer 1

k={0,1,2,3,4,5,6,7}
7*0+1=1
7*1+1=8
7*2+1=15
7*3+1=22
7*4+1=29
7*5+1=36
7*6+1=43
7*7+1=50
D={1,8,15,22,29,36,43,50}