Question

система уравней
2 (3x+2y)+9=4x+21
2x+10=3-(6x+5y)

Answer 1

2 (3x+2y)+9=4x+21,
2x+10=3-(6x+5y),

6х+4у+9 = 4х+21,
2х+10 =3-6х-5у,

2х+4у = 12,
8х+5у = -7,

х = (12-4у) : 2,

8*(12-4у) : 2 + 5у = -7,
96 - 16у + 5у = -7,
-11у = -7-96,
-11у = -103,
у = 9 4/11,

х = (12 - 4*9 4/11) : 2  = (132/11 - 412/11) : 2 = -280/11 : 2 =
= -280/22 = -12 8/11,

ответ:  (-12 8/11;  9 4/11)

Answer 2

Система уравней 
2 (3x+2y)+9=4x+21
2x+10=3-(6x+5y)

6x+4y+9=4x+21  2x+4y=17
2x+10=3-6x-5y    8x+5y=-7

8x+16y=68
8x+5y=-7         0+11y=68+7    11y=75      y=75/11
                        8x=-7-5y=-7-34 1/11=-41 1/11       8x=--41 1/11
                          x=-5 3/22