решите систему уравнений :
{ 4*(2х+5)=21+6х+4у,
9-3(4+у)=2(х+5)

4( 2х + 5 ) = 21 + 6х + 4y
8x + 20 = 21 + 6x + 4y
2x = 4y + 1
9 - 3( 4 + y ) = 2( x + 5 )
9 - 12 - 3y = 2x + 10
2x = - 3y - 13
4y + 1 = - 3y - 13
7y = - 14
y = - 2
2x = 6 - 13
x = - 7 : 2
x = - 3,5
Ответ ( - 3,5 ; - 2 )