Bonjour
A = (3 - 7/5) : (1 - 9/10)
A = [(3 x 5) / (1 x 5) - 7/5] : [(1 x 10) / (1 x 10) - 9/10}
A = (15/5 - 7/5) : (10/10 - 9/10)
A = 8/5 : 1/10
A = 8/5 x 10
A = 80/5
A = (5 x 16) / (5 x 1)
A = 16.
F = 7/- 8 + 5/6 : 4 - 1
F = - 7/8 + 5/6 x 1/4 - 1
F = - 7/8 + 5/24 - 1
F = (- 7 x 3) / (8 x 3) + 5/24 - (1 x 24) / (1 x 24)
F = - 21/24 + 5/24 - 24/24
F = - 45/24 + 5/24
F = - 40/24
F = (8 x - 5) / (8 x 3)
F = - 5/3.