Bonjour
a.4/3-(1/2+7/8)
= 4/3 - [(1 x 4)/(2 x 4) + 7/8]
= 4/3 - (4/8 + 7/8)
= 4/3 - 11/8
= (4 x 8)/(3 x 8) - (11 x 3)/(8 x 3)
= 32/24 - 33/24
= -1/24
b.4/3-7/5-(3/5-5/7)
= 4/3 - 7/5 - 3/5 + 5/7
= 4/3 - 7/5 - (3 x 7)/(5 x 7) + (5 x 5)/(7 x 5)
= 4/3 - 7/5 - 21/35 + 25/35
= 4/3 - (7 x 7)/(5 x 7) + 4/35
= 4/3 - 49/35 + 4/35
= 4/3 - 45/35
= 4/3 - (9 x 5)/(7 x 5)
= 4/3 - 9/7
= (4 x 7)/(3 x 7) - (9 x 3)/(7 x 3)
= 28/21 - 27/21
= 1/21
