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2014-03-22T20:38:20+01:00
bonsoir

23/18 x (3/4 + 5/12)
23/18 x (9/12 +5/12)
23/18 x 14/12
= 322/216 =161/108

(13/21 + 2/7) x (3/5 + 9/10)
(13/21 + 6/21) x ( 6/10 +9/10)
19/21 x 15/10
285/ 210  = 19/14

1 - (9/7 - 5/6 x 3/7)
1 - ( 9/7 - 15/42)
1 - ( 54/42 - 15/42)
1 - 39/42
42/42 - 39/42 = 3/42

3/2 - 2/3 x 1/5 + 24 x 1/30

3/2 - 2/15 + 24/30
45/30 - 4/30 +24/30
65/30 = 13/6

2014-03-22T21:17:26+01:00
23/18 x (3/4 + 5/12) = 23/18 x (3 x 3 / 4 x 3 + 5/12) = 23/18 x (9/12 + 5/12) = 23/18 x 14/12 = 322/216 = 2 x 161 / 2 x 108 = 161/108

(13/21 + 2/7) x (3/5 + 9/10) = (13/21 + 2 x 3 / 7 x 3) x (3 x 2 / 5 x 2 + 9/10) = (13/21 + 6/21) x (6/10 + 9/10) = 19/21 x 15/10 = 285/210 = 15 x 19 / 15 x 14 = 19/14

1 - (9/7 - 5/6 x 3/7) = 1 - (9/7 - 15/42) = 1 - (9 x 6 / 7 x 6 - 15/42) = 1 - (54/42 - 15/42) = 1 - 39/42 = 1 x 42 / 1 x 42 - 39/42 = 42/42 - 39/42 = 3/42 = 3 x 1 / 3 x 14 = 1/14

3/2 - 2/3 x 1/5 + 24 x 1/30
= 3/2 - 2/15 + 24 x 1/30 = 3/2 - 2/15 + 24/30 = 3 x 15 / 2 x 15 - 2 x 2 / 15 x 2 + 24/30 = 45/30 - 4/30 + 24/30= 65/30 = 5 x 13 / 5 x 6 = 13/6