tatsach (X-2/3=5/6x)
х-5/6x=2/3
-1/6x=2/3
x=2/3:(-1/6)=2/3*(-6)
x=-4

(1 4/5y=y+4)
1 4/5y-y=4
4/5y=4
y=4:4/5=4*5/4
y=5

(2/3y-1/3=5/9)
2/3y=5/9+1/3=5/9+3/9
2/3y=8/9
y=8/9:2/3=8/9*3/2
y=1 1/3

(3/4y-2/3=7/12) 
3/4y=7/12+2/3=7/12+8/12
3/4y=15/12
y=15/12:3/4=15/12*4/3
y=1 2/3