1)
{ (2x+1)/3 - (x-2y)/5 = 4(2x+y)/15 |*15
{ (x-4y)/3 + (5x-11y)/6 = (3x-1)/4 |*12
{ 5(2x+1) - 3(x-2y) = 4(2x+y)
{4(x-4y) + 2(5x-11y) = 3(3x-1)
{10x+5 - 3x +6y = 8x+4y
{4x-16y +10x-22y = 9x-3
{7x + 6y + 5 = 8x +4y
{14x - 38y = 9x- 3
{7x + 6y - 8x - 4y = - 5
{14x - 38y - 9x = -3
{-x + 2y = - 5 ⇒ x = 2y+5
{ 5x - 38y = -3
5(2y + 5) -38y = -3
10y + 25 -38y = -3
-28y = - 3 - 25
-28y = -28
y = 1
x= 2*1 + 5
x=7
ответ: (7; 1)
2)
{(7х +у) / 3 - (5х-у)/2 = (х+у) / 6 | *6
{ (9x-2y)/8 + (7x+4y)/6 = (x+y)/3 + 4 |*24
{2(7x+y) - 3(5x-y) = x+y
{3(9x-2y) + 4(7x+4y) = 8(x+y) + 4*24
{14x +2y -15x +3y = x+y
{ 27x -6y +28x +16y = 8x+8y +96
{-x + 5y = x+y
{55x +10y = 8x+8y +96
{ 5y -y = x+x
{ 55x +10y -8x - 8y =96
{ 4y = 2x ⇒ y = 2x/4 ⇒ y = 1/2 * x ⇒ y = 0.5x
{ 47x +2y =96
47x + 2 *0.5x = 96
47x + x=96
48x = 96
x= 96 :48
х= 2
у= 0,5*2
у=1
ответ : (2 ; 1)