Bonjour,
a) 2 + 1 : 6 + 1 : 24
= (2 x 24) / (1 x 24) + (1 x 4) / (6 x 4) + 1/24
= 48/24 + 4/24 + 1/24
= 53/24
b) 1 : 2 - 1 : 4 + 1 : 8
= (1 x 4) / (2 x 4) - (1 x 2) / (4 x 2) + 1/8
= 4/8 - 2/8 + 1/8
= 3/8
c) 8 : 9 x 27 : 4
= 216/36
= (36 x 6) / (36 x 1)
= 6.
d) 26 : 88 x 77 : 39
= 2 002/3 432
= (286 x 7) / (286 x 12)
= 7/12
e) 45 : 42 x 21 : 30
= 945/1 260
= (315 x 3) / (315 x 4)
= 3/4
f) 3 : 2 x 7 : 10 + 1 : 4 x 7 : 5
= 21/20 + 7/20
= 28/20
= (4 x 7) / (4 x 5)
= 7/5
g) (7 : 5 + 2 : 15) x 3 : 2
= [(7 x 3) / (5 x 3) + 2/15] x 3/2
= (21/15 + 2/15) x 3/2
= 23/15 x 3/2
= 69/30
= (3 x 23) / (3 x 10)
= 23/10.
h) 3 : 4 - 1 : 8 x 5 : 3
= 3/4 - 5/24
= (3 x 6) / (4 x 6) - 5/24
= 18/24 - 5/24
= 13/24.