X-1/2=3/4x; 1 4/5y=y+4; 3/4y-2/3=7/12y

1) $x- frac{1}{2} = frac{3}{4} x$
$x- frac{3}{4} x= frac{1}{2}$
$frac{1}{4}x= frac{1}{2}$
  x=2
2) $1 frac{4}{5} y=y+4$
$frac{1*5+4}{5} y-y=4$
$frac{4}{5} y=4$
y=5
3) $frac{3}{4} y- frac{2}{3} = frac{7}{12}y$
   $frac{3}{4} y- frac{7}{12}y = frac{2}{3}$
   $frac{3*3}{4*3} y- frac{7}{12} y= frac{2}{3}$
   $frac{9}{12} y- frac{7}{12} y= frac{2}{3}$
   $frac{2}{12} y= frac{2}{3}$
   $y= frac{2}{3} : frac{2}{12} = frac{2}{3} * frac{12}{2} = frac{1*4}{1*1} =4$
х=4