Question

A ={X | X ∈ N ,3 | X , X ≤ 21}
B ={x | x ∈ N , 5 | x , x ≤ 25}
C ={x | x ∈ N , 2 | x , x ≤ 20}

Answer 1

A={3,6,9,12,15,18,21}
B={5,10,15,20,25}
C={2,4,6,8,10,12,14,16,18,20}