Explications étape par étape:

a) -7/10 = -21/30. -11/15 = -22/30

-21/30 >-22/30. -7/10>-11/15

b)1/6 = 7/42. 4/21 = 8/42

7/42<8/42. 1/6<4/21

c) 3/8 = 15/40. 9/20 = 18/40

15/40<18/40. 3/8<9/20