Question 970684
{{{B=3+2A}}}
{{{A+B=9}}}
Substitute into eq. 2 from eq. 1,
{{{A+(3+2A)=9}}}
{{{3A=6}}}
{{{A=2}}}
Then,
{{{B=3+2(2)}}}
{{{B=3+4}}}
{{{B=7}}}