Bonjour
8/12 + 6/6 = 5/3
8/12 - 5/3 = 8/12 - (5 x 4) / (3 x 4) = 8/12 - 20/12 = - 12/12 = - 6/6
et
8/12 + 6/6 = 8/12 + 12/12 = 20/12 = 5/3