Qui peut m'aider a faire mon devoir maison je comprend rien :(

a = 4/15 +16/15 = 20/15 = 4/3

b = 12/21+2/21 = 14/21 = 2/3

c = 31/9 +5/9 = 36/9 =  4

d = 17/6 +23/6 = 40/6 =20/3
tu fais la meme chose pour les 2 autres c est simple

a = 4/3 -1/12 = 16/12-1/12 = 15/12

b = 21/8 -5/16 = 42/16 -5/16 = 37/16

c = 32/35 -4/7 = 32/35 -20/35 = 12/35

d = 9/10+7/5 = 9/10 +14/10 = 23/10

tu fais les 2 autres

a = 7/6 +((8/3-2/3) = 7/6 +(6/3) = 7/6 +12/6 = 19/6

b = (17/4-5/4) -3/4 =  12/4 -3/4 =9/4

c = (5/2-1/4) +(2-7/8) = (10/4-1/4) +(16/8 -7/8) =9/4 +9/8 = 18/8 +9/8 =27/8

je te laisse faire la derniere