Explicație pas cu pas:
1) a×b= 5/9×7/10=(5×7)/(9×10) =35/90= 7/18
b×a= 7/10×5/9=(7×5)/(10×9) =35/90= 7/18
b×c= 7/10×3/14=(7×3)/(10×14)=21/140=3/20
(a×b)×c= (5/9×7/10)×3/14=[(5×7)/(9×10)]×3/14= 35/90×3/14= 105/1260= 21/252
a×(b×c)= 5/9× 3/20= (5×3)/(9×20)= 15/180= 1/12
a×b×c= 5/9×7/10×3/14= (5×7×3)/(9×10×14)=105/1260= 21/252
2) a×b= 8/5×10/9=(8×10)/(5×9)= 80/45= 16/9
b×a=a×b
b×c= 10/9×3/4= (10×3)/(9×4)= 30/36=10/12=5/6
(a×b)×c= 16/9×3/4= (16×3)/(9/4)=48/36=8/6=4/3
a×(b×c)= 8/5×5/6= (8×5)/(5×6)= 40/30= 4/3
a×b×c= 8/5×10/9×3/4=(8×10×3)/(5×9×4)= 240/180=40/30=4/3
3) a×b= 2²/3³×9/2³= 4/27×9/8= 1/3×1/2= 1/6
b×a=a×b
b×c= 9/2³×6/5=( 9×6)/(8×5)= 54/40= 27/20
(a×b)×c= 1/6×6/5= 1/5
a×(b×c)= 4/27×27/20=1/5
a×b×c= 4/27×9/8×6/5=(se reduc) = 1/5
4)a×b= 2½×3⅕= 5/2×16/5= 8
b×a=a×b
b×c= 16/5×7/24=112/120= 56/60=14/15
(a×b)×c= 8×7/24=7/3
a×(b×c)=5/2×14/15=7/3
a×b×c= 5/2×16/5×7/24=7/3
