Réponse :
A = 5/4 x 3/7 =5x3/4x7 =15/28 =
B= 8/9x 4 = (8x4)/9 = 32/9
C=5/7 ÷ 9/2 =5/7 x 2/9 = 5x2 / 7x9 = 10/6 ( diviser une fraction c'est multiplier son inverse)
D = 1/4 ÷ 15/9 = 1/4 x 9/15 = 9x1/15x4 = 9/60
E= 4/5 + 7/5 = (4+7) / 5 = 11/5
F= 7/9 - 8/9 = (7-8)/9 = -1/9
G = 2/3 + 3/5 = 2x5 /3x5 + 3x3/5x3 = 10/15 + 9/15 = (10+9)/15 = 19/15
H= 6/7 - 8/9 = 6x9/7x9 - 8x7/9x7 =54/63 - 56/63 = (54-56)/63 = -2/63
I = 2/3 + 4 = 2/3 + 4/1 = 2/3 + 12/3 = (2+12)/3 = 14/3
J= 5 - 6/7 = 5/1 - 6/7 = 5x7/1x7 - 6/7 = 35/7 - 6/7 =(35-6)/7 = 29/7
K = -11/5 x 4/13 = -11x4 / 5x13 = -44/ 65
L = 10x 15/4 = 10x15/4 = 150/4 = 75/2
M = 4/6 ÷ 9/15 = 4/6 x 15/9 = 4x15/9x6 = 60/54 = 30x2/27x2 = 30/27 = 3x10/9x3 = 10/9
N = 7/9 ÷ 2/5 = 7/9 x 5/2 = 7x5/9x2 = 35/18
O = 2/7 ÷ 4/7 = 2/7 x 7/4 = 7x2/7x4 = 2/4
P = 3/8 - 15/8 = (3-15)/8 = -12/8
Q= 3/5 + 7/9 = 3x9/5x9 + 7x5/9x5 = 27/45 + 35/45 = (27+35) /45 = 62/45
R = 9/7 - 5/3 = 9x3/7x3 - 5x7/3x7 = 27/21 - 35/21 = (27-35)/21 = -8/21
S = 9/8 + 7 = 9/8 + 7/1 = 9/8 + 7x8/1x8 = 9/8 + 56/8 = 9+56 / 8 = 65/8
T = 6- 5/4 = 6/1 -5/4 = 6x4/1x4 - 5/4 = 24/4 - 5/4 = 19/4
voila:)
