Réponse :

-55/63*35/66 = -55*35/63*66 = -5*11*5*7/7*9*6*11 = -5*5/9*6 = -25/54

49/15*10/21 =) 7*7*5*2)/)5*3*7*3)= 7*2/3*3=14/9

-28/27*36/7 = (-28*36)/27*7 = (-4*7-6*6)/(3*9*7) = 36*4/3*9 = 144/27 = (9*16)/(3*9) = 16/3

-17/52*-39/34 =(17*39)/(52*34) = (17*13*3)/4*13*17*2) =3/8

Explications étape par étape :