Bonjour
C = (2/5 - 1/4 + 3) : (7/2 + 1/5)
C = [(2 x 4) / (5 x 4) - (1 x 5) / (4 x 5) + (3 x 20) / (1 x 20)] : [(7 x 5) / (2x 5) + (1 x 2) / (5 x 2)]
C = (8/20 - 5/20 + 60/20) : (35/10 + 2/10)
C = 63/20 : 37/10
C = 63/20 x 10/37
C = 630/740
C = (10 x 63) / (10 x 74)
C = 63/74.
