Question 1085080
{{{z=(X-mu)/sigma}}}
so
{{{-1=(28-mu)/sigma}}}
1.{{{28-mu=-sigma}}}
and
{{{-0.5=(34-mu)/sigma}}}
{{{-0.5sig,a=34-mu}}}
2.{{{-sigma=68-2mu}}}
Substitute from 1,
{{{28-mu=68-2mu}}}
{{{mu=68-28}}}
{{{mu=40}}}
Now use either equation to solve for {{{sigma}}}.