Chapter 3 - Section 3.2 - Problem Solving and Business Applications Using Systems of Equations - Exercise Set - Page 205: 19

$x=100,y=100$

As per the statement: $x+y=200$ and $0.05x+0.09y=(0.07)(200)$ After plugging the variable $x$ form the first equation in the second equation, we get $0.05(200-y)+0.09y=(0.07)(200) \implies 0.04y=4$ or, $y=100$ Now, $x+100=200 \implies x=100$ Thus, $x=100,y=100$