bonjour et merci de votre aide

bonjour
ex26
A=16x+7-9x+2
=16x-9x+7+2
=7x+9

B=5z+4.5-z+0.5
=5z-z+4.5+0.5
=4z+5

C=3+4t+12t-7t-3
=4t+12t-7t+3-3
=9t

D)5x²+4+2x²-1
5x²+2x²+4-1
7x²+3