Réponse :

bonjour

a = 4 x 12 = 48

a =  28 + 20 = 48

b = 12 + 15 = 27

b =  3 ( 4 + 5) = 3 x 9 = 27

c = 13 x 2 = 26

c = 16 + 10 = 26

d = 70 - 14 =  56

d = 7 ( 10 - 2 ) =  7 x 8 = 56

e = 5 x 6 = 30

e = 40 - 10 = 30

f = 680 - 280 = 400

f = 20 ( 34 - 14 ) = 20 x 20 = 400

Explications étape par étape :