a) A = { 5,6,7 }
A = { $x∈{N}$ ║ $4< x ≤ 7^{}$ }
c ) A = { 11,12,13,14,15,16,17,18,19,20 }
A = { $x∈{N}$ ║ $11≤ x ≤ 20^{}$ }
d) A = { 10,11,12,13,14,15 }
A = { $x∈{N}$ ║ $ 9< x ≤ 15^{}$ }
e) A = { 0,1,2,3,4,5,6,7,8,9,10,11,......,27,28,29,30 }
A = { $x∈{N}$ ║ $0≤ x ≤ 30^{}$ }