There exist real numbers t and s such that \(\begin{pmatrix} -1 \\ \phantom -5 \end{pmatrix} + t \begin{pmatrix} \phantom -3 \\ -4 \end{pmatrix} = \begin{pmatrix} 0 \\ 4 \end{pmatrix} + s \begin{pmatrix} -5 \\ \phantom -2 \end{pmatrix}.\)Find t + s.
s = 1/7 and t = -4/7, so s + t = -3/7.
