Répondre :
x = 3/7 ÷ 4/9 = 3/7 x 9/4 = 27/28
y = 3/(7/(4/9)) = 3/(7 x 9/4) = 3/(63/4) = 3 x (4/63) = 12/63 = 4/21
z = y
t = (3/(7/4))/9 = (3 x 4/7)/9 = (12/7)/9 = 12/7 x 1/9 = 12/63 = 4/21
s= ((3/7)/4)/9 = (3/7 x 1/4)/9 = (3/28)/9 = 3/(28 x 9) = 1/(28x 3) = 1/84
y = 3/(7/(4/9)) = 3/(7 x 9/4) = 3/(63/4) = 3 x (4/63) = 12/63 = 4/21
z = y
t = (3/(7/4))/9 = (3 x 4/7)/9 = (12/7)/9 = 12/7 x 1/9 = 12/63 = 4/21
s= ((3/7)/4)/9 = (3/7 x 1/4)/9 = (3/28)/9 = 3/(28 x 9) = 1/(28x 3) = 1/84