La exercitiul 5 :
a x (b x c) =a x b x c si fiindca a x b=6/13 rezulta ca :
a x b x c= 6/13 x 2intregisi3/5=6/13 x 13/5
a x b x c=6/13 x 13/5
a x b x c=6/5 a x (b x c )=1,2
la exercitiul 6
(a x b)x c =a x b x c=1,2(5)x67/113=115/90 x 67/113=1541/2034
a x b x c =1541/2034
(a x b) x c=1541/2034
