B)
{x-y=2
{1/2x-1=1/4y /*(-2)
{x-y=2
{-x+½y=-2
___________
-½y=0
y=0
x=2
c)
{-x-y=2
{2(3x+y)=-20
{-6x-6y=12
{6x+2y=-20
__________
-4y=-8
y=2
x=-4
d)
{4x+3y=54
{1/3x=4(1+1/8y) /*12
{4x+3y=54
{-4x+6y=-48
___________
9y=6
y=⅔
x=13
chyba dobrze jak cos to pisz do mnie;) pozdrawiam Kromcia