当 x > 2 时
x - 2 + 2x + 1 = 7
x = 8/3
当 x < -1/2 时
2 - x - 2x - 1 = 7
x = -2
当 -1/2 ≤ x ≤ 2 时
2 - x + 2x + 1 = 7
x = 4(舍去)
综上：x = -2 或 x = 8/3