Bonjour,
A = - 1/5 * 4/3 + 7/2 = -4/15 + 7/2 = (-4*2 + 7*15)/(15*2) = 97/30
B = (3/2 + 3/5) (5/4 - 4/3) = ((5*3 + 3*2)/(2*5)) ((5*3 - 4*4) / (4*3))
B = 21/10 * (-1/12) = - (3*7)/(3*8*5) = -7/40
C = 13/7 + 8/7 * 5/4 = 13/7 + (2*5/7) = 23/7
D = 7/3 - (3*2*5)/(2*3*7) = 7/3 - 5/7 = (49 - 15) / 21 = 34/21
