Question 849929
{{{(A+B)/2=20}}}
1.{{{A+B=40}}}
.
.
2.{{{A-4=2B}}}
so
{{{A=2B+4}}}
Substituting into the first equation,
{{{2B+4+B=40}}}
{{{3B=36}}}
{{{B=12}}} 
and then,
{{{A+12=40}}}
{{{A=28}}}