je ne comprend pas aussi cette exercice Aidez-moi please (svp) Merci d'avance

A = x + 3 + 4x - 5
A = 5x - 2

B = 6 - 2t - 4t + 8
B = - 6t + 14

C = - 8a - 3 - 4a
C = - 12a - 3

D = 3y + 7- 5y + 3
D = - 2y + 10

E = 5z - 6 - 7 + 2z + 3z
E = 10z - 13

F = 3 - 4x + 2x - 8
F = - 2x - 5

a) (x+3)+ (4x-5)= x+3+4x-5=5x-2
b) 6-2t-(4t-8)=6-2t-4t+8=14+6t
c)-(8a+3)-4a=-8a-3-4a=12a-3
d) (3y+7)+(-5y+3)=3y+7-5y+3=-2y+10
e)5z-6-(7-2z)+3z=5z-6-7+2z+3z=10z+13
f)(3-4x)-(-2x+8)=3-4x+2x-8=-2x-5