Répondre :
Ex 3:
A=2/3+1/4-5/9
=24/36+9/36-20/36
=13/36
B=1/2-4/6-6/8-2/4+2/3+3/4
=1/2-2/3-3/4-1/2+2/3+3/4
=0
C=9/4-9/3-54/2
=9/4-3-27
=9/4-30
=9/4-120/4
=-111/4
A=2/3+1/4-5/9
=24/36+9/36-20/36
=13/36
B=1/2-4/6-6/8-2/4+2/3+3/4
=1/2-2/3-3/4-1/2+2/3+3/4
=0
C=9/4-9/3-54/2
=9/4-3-27
=9/4-30
=9/4-120/4
=-111/4