aider moi Svp pour la 16 merci d'avance !!

ex 16:
a) 14/27 x 18/35
=(14x18)/(27x35)
=(7x2x9x2)/(3x9x5x7)
=4/15

b) 30/8x12/54
=(30x12)/(8x54)
=(6x5x4x3)/(4x2x6x9)
=5/6

c) 56/9x15/42
=(56x15)/(9x42)
=(7x8x3x5)/(3x3x6x7)
=20/9

d) 72/64x8/45
=(72x8)/(64x45)
=(8x9x8)/(8x8x5x9)
=1/5