7 chia hết (x + 1)
=> x + 1 = -1
=> x + 1 = 1
=> x + 1 = 7
=> x + 1 = -7
=> x = -2, 0, 6, -8
18 chia hết (3 - x)
=> 3 - x = 1
=> 3 - x = -1
=> 3 - x = 3
=> 3 - x = -3
=> 3 - x = 6
=> 3 - x = -6
=> 3 - x = 18
=> 3 - x = -18
=> x = 2, 4, 0, 6, -3, 9, -15, 21
24 chia hết (x - 5)
=> x - 5 = + - 1
=> x - 5 = + - 2
=> x - 5 = + - 3
=> x - 5 = + - 4
=> x - 5 = + - 6
=> x - 5 = + - 8
=> x - 5 = + - 12
=> x - 5 = + - 24
=> x = -19, -7, -3, -1, 1, 2, 3, 4, 6, 7, 8, 9, 11, 13, 17, 29
Vậy x = 6