A = -5/9 - 1/12
=-20/36-3/36
=-23/36
B =4/15- 3/18
=24/90-15/90
=9/90
=1/10
C=-4/15+7/55
=-220/825+105/825
=-115/825
=-23/165
D= 4/7- -2/3
=4/7+2/3
=12/21+14/21
=26/21
E =4 - 2/-11
=4+2/11
=44/11+2/11
=46/11
F= 2/45 --7/-30
=2/45-7/30
=4/90-21/90
=-17/90
exercice 2
D= (-4 /5 + 2/3) - (5/3-14/5) -(3/7+2)
=-4/5+2/3-5/3+14/5-3/7-2
=10/5-3/3-3/7-2
=2-1-3/7-2
=-1-3/7
=-7/7-3/7
=-10/7
E=-4-(-2/5+3)+(5 + 4/3) - (4/5 -2/3)
=-4+2/5-3+5+4/3-4/5+2/3
=-2-2/5+6/3
=-2-2/5+2
=-2/5