Chapter 5, Systems of Equations and Inequalities - Section 5.1 - Systems of Linear Equations in Two Variations - 5.1 Exercises - Page 447: 60

$18,6$.

Let $x,y$ be these numbers. Then we know that $x=2y+6,x+y=2(x-y)=2x-2y$. The second equation can be written as $x+y=2x-2y\\3y=x$. Thus, plugging this back into the first equation, we get: $2y+6=3y\\6=y$ Then $x=2y+6=2*6+6=18$.