Question 893370
{{{A=3B-9}}}
{{{A+2B=16}}}
Substitute for {{{A}}},
{{{(3B-9)+2B=16}}}
{{{5B=25}}}
{{{B=5}}}
Then,
{{{A=3(5)-9}}}
{{{A=15-9}}}
{{{A=6}}}