Bonsoir
a.4/3-(1/2+7/8)
= 4/3 - [(1 x 2) / (2 x 4) + 7/8]
= 4/3 - (2/8 + 7/8)
= 4/3 + 9/8
= (4 x 8) / (3 x 8) + (9 x 3) / (8 x 3)
= 32/24 + 27/24
= 59/24
b.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 - 7/5 - (- 4/35)
= 4/3 - 7/5 + 4/35
= (4 x 35) / (3 x 35) - (7 x 21) / (5 x 21) + (4 x 3) / (35 x 3)
= 140/105 - 147/105 + 12/105
= 5/105
= (5 x 1) / (5 x 21)
= 1/21.
