2x+10=9-(4+y)
21+6x+4y=4(2x+5)
2x+10=9-(4+y)
2x+10=9-4-y
у=5-10-2х
у=-5-2х
у=-(5+2х)
21+6x+4y=4(2x+5)
21+6x+4y=8x+20
4у=8х-6х+20-21
4у=2х-1
4у=2х-1
4(-(5+2х))=2х-1
-20-8х=2х-1
2х+8х=1-20
10х=-19
х=-19/10
х=-1,9
у=-(5+2х)= -(5+2*(-1,9))= -(5-3,8)= -1,2