Chapter 3 - Section 3.1 - Systems of Linear Equations in Two Variables - 3.1 Exercises - Page 228: 67

$x=-3$ $y=2$

If we add the two equations, we can eliminate the $y$ from the system: $3x+y=-7$ $x-y=-5$ $3x+x=-12$ $x=-3$ $3(-3)+y=-7$ $y=2$ We have to check, if the solution is right. Substitute $x$ with -3 and $y$ with 3: $3(-3)+2=7$ $\checkmark$ $-3-2=-5$ $\checkmark$