Coucou
A = 7/4 + 2/3 x 15/8
= 7/4 + (2 x 15) / (3 x 8)
= 7/4 + (2 x 3 x 5) / (3 x 2 x 4)
= 7/4 + 5/4
= (7 + 5) / 4
= 12 / 4
= (3 x 4) / 4
= 3
B = (3 - 3/5) / (-2/3 - 4/5)
= [ (3 x 5) / (1 x 5) - 3/5 ] / [ (-2 x 5) / (3 x 5) - (4 x 3) / (5 x 3) ]
= [ 15/5 - 3/5 ] / [ -10/15 - 12/15 ]
= [ (15 - 3) / 5 ] / [ (-10 - 12) / 15 ]
= (12 / 5) / (-22 / 15)
= (12 / 5) x (15 / -22)
= (12 x 15) / (5 x -22)
= - (2 x 6 x 3 x 5) / (5 x 11 x 2)
= - (18 / 11)
Voilà j'espère avoir pu t'aider ^^
N'hésite pas si tu as des questions :)
