\( \vec{s}=4 \cdot \vec{a}+8 \cdot \vec{b}-4 \cdot \vec{c} \)
\( \vec{s}=4 \cdot \left(\begin{array}{l} 2 \\ 3 \\ 4 \end{array}\right) +8 \cdot \left(\begin{array}{l} 3 \\ 0 \\ 1 \end{array}\right)-4 \cdot \left(\begin{array}{c} -4 \\ 1 \\ 5 \end{array}\right) \)
\( \vec{s}= \left(\begin{array}{l} 8 \\ 12 \\ 16 \end{array}\right) + \left(\begin{array}{l} 24 \\ 0 \\ 8 \end{array}\right)+ \left(\begin{array}{c} 16 \\ -4 \\ -20 \end{array}\right) \)
\( \vec{s}= \left(\begin{array}{l} 48 \\ 8 \\ 4 \end{array}\right) \)