Réponse:
A=3/5+2/5×4/7
A=3/5+2×4/5×7
A=3/5+8/35
A=3×7/5×7+8/35
A=21/35+8/35
A=29/35
B=(7/4-1/3)×(1/5+3/10)
B=(7×3/4×3-1×4/3×4)×(1×2/5×2+3/10)
B=(21/12-4/12)×(2/10+3/10)
B=17/12×5/10
B=17×5/12×10
B=85/120
B=17×5/24×5
B=17/24
C=(2-7/9)÷2/3
C=(18/9-7/9)÷2/3
C=11/9÷2/3
C=11/9×3/2
C=11×3/9×2
C=33/18
C=11×3/3×6
C=11/6
