a) Ta có: 10 < x < 99
=> x \(\in\){11; 12; 13; 14; .....; 98}
=> A = {11; 12; 13; 14; ...; 98}
b) Ta có : x \(⋮\)4 => x \(\in\)B(4) = {0; 4; 8; 12; 16; ....;96}
Do 0 < x < 100 => x \(\in\){4; 8; 12; 16; ....; 96}
=> B = {4; 8; 12; 16; ...; 96}
c) Ta có: x + 5 = 10 => x = 10 - 5 = 5
=> C = {5}
d) Ta có: 2x + 5 = 17
=> 2x = 17 - 5
=> 2x = 12
=> x = 12 : 2 = 6
=> D = {6}