1) 5x - 16 = 40 + x 2) 4x - 10 = 15 - x
=> 5x - x = 40 + 16 => 4x + x = 15 + 10
=> 4x = 56 => 5x = 25
=> x = 56 : 4 => x = 25 : 5
=> x = 14 => x = 5
3) 3x - 6 = 5x + 2
=> 3x - 5x = 2 + 6
=> -2x = 8
=> x = 8 : (-2)
=> x = -4
4) 15 - x = 4x - 5
=> 15 + 5 = 4x + x
=> 25 = 5x
=> x = 25 : 5
=> x = 5
5) x - 15 = 6 + 4x
=> x - 4x = 6 + 15
=> -3x = 21
=> x = 21 : (-3)
=> x = -7
còn lại tự làm