Bonsoir,
nbre choisi: x
PA
x
x+4
7(x+4) = 7x+28
7x+28 - 3x = 4x-28
PB
-4x
-4x+19
4x-28 = -4x+19
4x+4x = 19 +28
8x = 47
x = 47/8 =5,875