bonsoir
a = 4/3 - ( 4/8 + 7/8 ) = 4 /3 - 11 /8 = 32/24 - 33/24 = - 1 /24
b = 4/3 - 7/5 - ( 21/35 - 25/35 )
= 4/3 - 7/5 + 4/35
= 140/105 - 147/105 + 12/105
= 5/105 = 1 /21
