вампир999 .......................

отличнно 5y+7(3-y)=3(5-2y)-6
5y+21-7y=15-6y-6
5y-7y+6y=15-6-21
4y=-12
y=-12:4
y=-3

7y-4(3y+5)=2-3(4y-9)
7y-12y-20=2-12y+27
7y-12y+12y=2+27+20
7y=49
y=49:7
y=7