1) (х-5)/4=(21-2х+11)/3
(х-5)/4=(32-2х)/3
(х-5)*3=(32-2х)*4
3х-15=128-8х
3х+8х=128+15
11х=143
х=143:11
х=13
2)(7х-12)/3=х+13-5
7/3*х-12/3=х+8
7/3х-4=х+8
7/3х=х+12
7/3х-х=12
4/3х=12
х=12*3:4
х=9
3)(2-7y+2*(4y+7))/6=-y/2
(2-7y+8y+14)=-y*6:2
y+16=-3y
4y=-16
y=-4