bonjour
exercice 1
stylo = x
cahier = x + 0.3
colle = 2 ( x + 0.3) = 2 x + 0.6
montant des achats = 3 x + 5 ( x + 0.3) + 2 ( 2 x + 0.6)
= 3 x + 5 x + 1.5 + 4 x + 1.2
= 12 x + 2.7
stylo = 1 €
cahier = 1.30 €
colle = 2.60 €
montant : 12 x + 2.7 = 12 + 2.7 = 14.7 €
exercice 2
périmètre carré = 4 ( 3 x + 5 ) = 12 x + 20
périmètre rectangle = 2 ( 3 + 2 x - 7) = 2 ( 2 x - 4) = 4 x - 8
exercice 3
3 ( x + 4) - 7 = 5 ( x + 1) - 2 x
pour x = 1
3 ( 1 + 4) - 7 = 5 ( 1 + 1) - 2
= 15 - 7 = 10 - 2
8 = 8
pour x = 7
( 3 * 11) - 7 = (5 * 8) - 14
33 - 7 = 26
26 = 26
3 x + 12 - 7 = 5 x + 5 - 2 x
3 x + 5 = 3 x + 5
pam = x
Pim = x + 2
Poum = x + 2 + 3 = x + 5
toto = 2 ( x + 2) = 2 x + 4
x + x + 2 + x + 5 + 2 x + 4 = 31
5 x = 31 - 2 - 5 - 4
5 x = 20
x = 4
Pam a 4 ans, Pim 6 ans, Poum 9 ans et Toto 12 ans
