C = 127 - (127 - x) + 23 + 5 × x
= 127 - 127 + x + 23 + 5 × x
= 0 + x + 23 + 5 × x
= (x + 5 × x) + 23
= 6x + 23
D = 107 - (107 + 2x - 23) + 4 × x
= 107 - 107 - 2x + 23 + 4 × x
= 0 - 2x + 23 + 4x
= (-2x + 4x) + 23
= 2x + 23
E = x + 21 + (-10) + 2 - x + 5 × x
= (x - x + 5x) + (21 - 10 + 2)
= (0 + 5x) + (11 + 2)
= 5x + 13