Bonjour,
1)
A = 2/3 - 2/3 x 9/5
A = 2/3 - 18/15
A = 2 x 5 / 3 x 5 - 18/15
A = 10/15 - 18/15
A = - 8/15
B = (1/3 - 1/6) : 2/3
B = (1 x 2 / 3 x 2 - 1/6) : 2/3
B = (2/6 - 1/6) : 2/3
B = 1/6 : 2/3
B = 1/6 x 3/2
B = 3/12
B = 3 x 1 / 3 x 4
B = 1/4
3) L'inverse de A = - 15/8