a) cinq sixieme + neuf huitieme - 1 b) neuf quart x six tiers x 2

A)
5/6+9/8-1=
40/48+54/48-48/48 = 46/48 = 23/24

B)
9/ 4 x 6 /3 x 2= 108 / 12 = 36 / 4 = 9

A ) 5/6 + 9/8 - 1
= 5 x 6 / 6 x 8 + 9 x 6 / 8 x 6 - 1 x 48 / 1 x 48
= 30/48 + 54/48 - 48/48
= 36/48
= 12 x 3 / 12 x 4
= 3/4

b) 9/4 x 6/3 x 2
= 54/12 x 2
= 108/12
= 12 x 9 / 12 x 1
= 9