Bonjour pouvez vous m’aidez merci d’avance

Bonjour,

a + b = 8
+. +
c - d = 6
=. =
13. 8

a + b = 8
a + c = 13
b + d = 8
c - d = 6

a + b = 8 => b = 8 - a
b + d = 8 => b = 8 - d

8 - a = 8 - d
d = a

a + c = 13
c - d = 6 => on remplace d

c = 13 - a
c = 6 + a

On additionne les deux équations :
2c = 13 + 6 - a + a
2c = 19
c = 19/2
c = 9,5

On remplace c :
c = 6 + a
a = 19/2 - 6
a = 19/2 - 12/2
a = 7/2
a = 3,5

d = a = 7/2 = 3,5

a + b = 8
b = 8 - a
b = 8 - 7/2
b = 16/2 - 7/2
b = 9/2 = 4,5

7/2 + 9/2 = 8
+. ....+
19/2 - 7/2 = 6
=...... =
13..........8