Question

X+y+z=20
2x-3y-z=0
2x-2y-z=5

Answer 1

{X+y+z=20
{2x-3y-z=0
{2x-2y-z=5
:
:
{x=20-y-z
{2x-3y-z=0
{2x-2y-z=5
:
:
{2*(20-y-z) - 3y - z=0
{2*(20-y-z) - 2y - z = 5
:
:
{ -5y - 3z = -40
{ 4y + 3z=35
-----------------------(+)
-y = - 5 *(-1)
y=5



- 4y - 3z = -35

- 4*5 - 3z = -35

-20 - 3z = -35

-3z = -35 + 20

-3z = -15

z = 15/3


z= 5



x = 20 - 5 - 5


x= 10



( x , y , z ) = ( 10 , 5 , 5 )