Determine the point at which these two lines intersect: $\begin{array}{l}y=-x-3 \\ y=3 x\end{array}$

Step 1 ：Set the two equations equal to each other: -x - 3 = 3x

Step 2 ：Solve for x to get \(x = -\frac{3}{4}\)

Step 3 ：Substitute \(x = -\frac{3}{4}\) into either of the original equations to find the corresponding y-coordinate, which is \(y = -\frac{9}{4}\)

Step 4 ：The point of intersection of the two lines is \(\boxed{\left(-\frac{3}{4}, -\frac{9}{4}\right)}\)