bonjour,
A = mets des parenthèses que l'on comprenne
B = ( 1/3 - 1/5) x 2/5 = ( 5/15 - 3/15) x 2/5 = 2/15 x 2/5 = 4/75
C = 5/4 - 9/13 x 65/81 + 11/36
C = 5/4 - 585/1053 + 11/36 = 5/4 - 5/9 + 11/36
= 45/36 - 20/36 + 11/36 = 14/36 = 7/18
d = 13/5 x ( 19/26 - 2/13) = 13/5 x ( 19/26 - 4/26)
= 13/5 x 15/26 = 195/130 = 3/2