3) \( \begin{array}{l}y=3 x-19 \\ -x-2 y=-18\end{array} \)

To solve the system of equations given by \( y = 3x - 19 \) and \( -x - 2y = -18 \), you can substitute the expression for \( y \) from the first equation into the second one. After substituting, you should be able to isolate \( x \) and find its value. Once you've found \( x \), plug it back into the first equation to get \( y \). As you work through these equations, keep an eye out for mistakes like sign errors or forgetting to distribute correctly when substituting! After you’ve solved for \( x \) and \( y \), consider how these linear equations might represent relationships in real life, like predicting expenses based on income changes or finding breakeven points in business scenarios—mathematics can be quite useful beyond the classroom!