Vous pouvez me faire le 1 svp

42/840 = 42 /42x20 = 1/20

12/80 = 4x3 / 4x20 = 3/20

21/70 = 7x3 =7x10 = 3/10

56/800 =  8x7 / 8x100 = 7/100

39/150 =  3x13 / 3x50 = 13/50

5/250 = 5/5x50 = 1/50

90/600 = 9/60 = 3x3 /3x20 = 3/20