calculer et simplifier A=7/3+8/21 B=3/2*4/5*6/7 C=28/45*50/70 DD=(17/12-1/6)-(3/4-1/2) E=3-1/5*25/7 F=(1/6+5/2)*5/12-1/3)

A=7/3+8/21
A=7x7/3x7+8/21
A=49/21+8/21
A=57/21

B=3/2*4/5*6/7
B=3x4x6/2x5x7
B=3x2x6/5x7
B=36/35

C=28/45*50/70
C=28x50/45x70
C=4x7x5x10/9x5x7x10
C=4/9

D=(17/12-1/6)-(3/4-1/2)
D=(17/12-2/12)-(3/4-2/4)
D=15/12-(1/4)
D=15/12-3/12
D=12/12
D=1

E=3-1/5*25/7
E=3-25/5x7
E=3-5/7
E=21/7-5/7
E=(21-5)/7
E=16/7

F=(1/6+5/2)*5/12-1/3)
F=(1/6+15/6)(5/12-4/12)
F=16/6+1/12
F=16x2/12+1/12
F=32/12+1/12
F=33/12
F=11/4