bonjour
A = 12/5 - 3/5 x 7/9
= 12/5 - 21/45
= 108/45 - 21/45
= 87 /45 = 29/15
B = 3/2 x ( 1/3 - 5/4 )
= 3/2 x ( 4/12 - 15/12)
= 3/2 x - 11 /12
= - 33 /24 = - 11 / 8
C = ( 6/6 + 5/6 ) : ( 24/12 - 5 /12 )
= 13 /6 : 19/12
= 13/6 x 12/19
= 156/114 = 26/19