Question 883951
{{{A=(1/2)bh=42}}}
{{{b(b+5)=84}}}
{{{b^2+5b-84=0}}}
{{{(b-7)(b+12)=0}}}
Two solutions but only the positive one makes sense here.
{{{b-7=0}}}
{{{b=7}}}
{{{h=7+5=12}}}