Réponse:
a.1-2/7=1/1×7/2=7/2
b.5÷2/7=5/1×7/2=35/2
c.2×2/7÷-3/4=4/14÷-3/4=4/14×4/-3=16/42=1/3
d.-3/4÷-3×5=-3/4÷15=-3/4×1/-15=-3/-60
e.1/5-1÷-3/4=1/5-(1/1×4/-3)=1/5-4/-3=3/15-(-20/15)=23/15
f.5+2/7÷-3/4=35/7+2/7÷-3/4=37/7÷-3/4=37/7×4/-3=148/-21
g.2/7÷-3/4-5=2/7÷(-3/4-20/4)=2/7÷-23/4=2/7×4/23=8/161.
