Matrices Solving

Let ${A} = \begin{pmatrix} 0 & 5 & 7 \\ -2 & 7 & 7 \\ -1 & 1 & 4 \end{pmatrix}$. Find all values of $t$ such that $\det (t{I} - {A}) = 0$, where $I$ is the $3 \times 3$ identity matrix.