documentclass{article}
usepackage{empheq}
usepackage{cases}% http://ctan.org/pkg/cases


begin{document}

begin{subnumcases}{x=}
  a + b \
  c + d \
  e + f
end{subnumcases}


begin{equation}
epsilon_{(3,2)} = left{ begin{array}{lcr}
  x(z) &=& z^2 - 2,v \
  y(z) &=& z^3 - 3,v,z \
  t_1 &=& 3,v^2
end{array} right.
end{equation}

begin{subnumcases}{epsilon_{(2,3)}=}
  x(z) = z^2 - 2,v label{eq1asfsafs} \
  y(z) = z^3 - 3,v,z label{eqjfdklsafjasfkasjf}\
  t_1 = 3,v^2 label{ejfklasjfkldsjafkl}
end{subnumcases}

begin{subequations}
label{fdjfdsadadasad}
begin{empheq}[left={x=}empheqlbrace]{align}
   x(z) &=& z^2 - 2,v label{eq1asfsafs} \
   y(z) &=& z^3 - 3,v,z label{eqjfdklsafjasfkasjf}\
   t_1 &=& 3,v^2 label{ejfklasjfkldsjafkl}
end{empheq}
end{subequations}



end{document}