C'est pour l'exercice 3et4 svp!

3)
A = 4/15+ 16/15
A = 20/15
A = 5 x 4 / 5 x 3
A = 4/3

B = 28/8 - 2
B = 28/8 - 2 x 8 / 1 x 8
B = 28/8 - 16/8
B = 12/8
B = 4 x 3 / 4 x 2
B = 3/2

C = 4/3 - 1/12
C = 4 x 4 / 3 x 4 - 1/12
C = 16/12 - 1/12
C = 15/12
C = 3 x 5 / 3 x 4
C = 5/4

D = 14/9 x 2,7
D = 37,8/9
D = 37,8 x 10 / 9 x 10
D = 378/90
D = 18 x 21 / 18 x 5
D = 21/5

E = 15/4 x 8/25
E = 120/100
E = 20 x 6 / 20 x 5
E = 6/5

4)
Lundi : 1/12
Mardi : 1/12
Mercredi : 1/12
Jeudi : 1/12
Vendredi : 1/12
Samedi : 1/3
Dimanche : il termine

Quelle fraction de la surface Mathieu devra peindre dimanche ?

1 - ((5 x 1/12) + 1/3)
= 1 x 12 / 1 x 12 - (5/12 + 1 x 4 / 3 x 4)
= 12/12 - (5/12 + 4/12)
= 12/12 - 9/12
= 3/12
= 3 x 1 / 3 x 4
= 1/4
Mathieu peindra 1/4 de la surface le dimanche

bonjour

Exercice 3

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

b = 28/8 - 2 = 28/8 - 16/8 = 12/8 = 3/2

c = 4/3 - 1/12 = 16/12 - 1 /12 = 15/12 = 5/ 4

d = 14/9 x 2.7 = 37,8/9 = 378/90 = 21/5

e = 15/4 x 8/25 = 120/100 = 6/5

Exercice 4 

du lundi au vendredi , il y a 5 jours
5 x 1/12 = 5/12 ,
samedi : 1/3
peint du lundi au samedi = 5/12 + 1/3 = 5/12 + 4/12 = 9/12 ou 3/4
dimanche il restera : 1/4