So,

\(\begin{cases}x + y = 3\\xy = -18\end{cases}\)

You can check by calculating the sum and product that x = 6, y = -3 is a solution.

Alternatively, if you know how to solve a quadratic equation, by Vieta's formula, x and y are the roots of \(t^2 - 3t - 18 = 0\).