Bonjour,
a/
1/9 -15/9 ×1/6=( 1/9) -(15/54)
=[(1×6)/(9×6)]-(15/54)
= (6/54)-(15/54)
=-9/54
=(9×(-1))/(9×6)
= -1/6
b/
7/3-2/3÷8/7=(7/3)-(2/3)×(7/8)
= (7/3)-[(2×7)/(3×8)]
= (7/3)-(14/24)
=[(7×8)/(3×8)]-(14/24)
=(56/24)-(14/24)
= 42/24
=(3×14)/(8×3)
=14/3
pour les autre expression je les ai pas bien compris