Bonjour
A =- 1 + 7/- 12 : (1 - 1/3) : 6
A = - 1 - 7/12 : [(1 x 3) / (1 x 3) - 1/3] : 6
A = - 1 - 7/12 : (3/3 - 1/3) : 6
A = - 1 - 7/12 : 2/3 : 6
A = - 1 - 7/12 x 3/2 x 1/6
A = - 1 - 21/24 x 1/6
A = (- 1 x 144) / (1 x 144) - 21/144
A = -- 144/144 - 21/144
A = - 165/144
A = (3 x - 55) / (3 x 48)
A = - 55/48.