bonsoir
73
a/5/12-5/3+1/6-2/9=15/36-60/36+6/36-8/36=-47/36
b/3/7+3/4-5/2-17/8=24/56+42/56-140/56-119/56=-193/56
74 a/2-1/3+1/6-1/9=36/18-6/18+3/18-2/18=31/18
b/1+1/2+3/4+5/6=12/12+6/12+9/12+10/12=37/12
75 a/4/3-(1/2+7/8)=4/3-(8/16+14/16)=4/3-22/16=4/3-11/8=32/24-33/24=-1/24
b/4/3-7/5-(3/5-5/7)=4/3-7/5-(21/35-25/35)=4/3-7/5-(-4/35)=4/3-7/5+4/35=140/105-147/105+12/105=5/105=1/21
