Bonsoir pouvez-vous me faire l’exercice 5 et 6 je n’y arrive pas merci

Bonjour,
a)
16/28 = 4/7
b)
-10/18 = - 5/9
c)
-63/36 = - 7/4
d)
10/60 = 1/6
e)
-6/30 = -1/5
f)
-56/120 = -28/60 = -14/30 =-7/15
exercice 6
7/5 de tours -> 2/3mm
1/5 -> (2/3 )/7
1 tour: (2/3*5)/7
3 tours -> (2/3*3*5)/7 = (30/3)/7 =10/7 =>1,43mm