determinati numerele x si y stiind ca x+y=12 si x+z=5 calculati 5x+2y-3z

Răspuns :

x+y=12
y=12-x
x+z=5
z=5-x
5x+2(12-x)-3(5-x)
=5x+24-2x-15+3x
=6x+9
=3(2x+3)