Решить 1 {3x+4y=0 {2x+3y=1 2 {4x-3y=7 {5x+2y=26 3 {3x-5y=0 {8y-5x=-1

1. 
{3x+4y=0
{2x+3y=1

{3x+4y=0
{x=(1-3y)/2

3(1-3y)/2+4y=0
3(1-3y) + 8y = 0 
3 - 9y + 8y = 0
y = 3
x= (1-3y)/2=(1-9)/2=-4

2.
{4x-3y=7
{5x+2y=26

{x=(3y+7)/4
{5(3y+7)/4+2y=26

{x=(3y+7)/4
{5(3y+7)+8y=104

{x=(3y+7)/4
{15y+35+8y=104

{x=(3y+7)/4
{23y=104-35=69

{x=(3y+7)/4
{y=3

x=(3*3+7)/4=4

3.
{3x-5y=0
{8y-5x=-1

{x=5y/3
{8y-5x=-1

{x=5y/3
{8y-5*5y/3=-1

{x=5y/3
{24y-25y=-3

{x=5y/3
{y=3

x=5y/3=5*3/3=5