Answer
$$\left\langle {20, - 26, - 11} \right\rangle $$
Work Step by Step
$$\eqalign{
& {\text{Let }}{\bf{u}} = \left\langle {2,4, - 5} \right\rangle {\text{ and }}{\bf{v}} = \left\langle { - 6,10,2} \right\rangle \cr
& {\bf{u}} - 3{\bf{v}} = \left\langle {2,4, - 5} \right\rangle - 3\left\langle { - 6,10,2} \right\rangle \cr
& {\text{Multiply}} \cr
& {\bf{u}} - 3{\bf{v}} = \left\langle {2,4, - 5} \right\rangle - \left\langle { - 18,30,6} \right\rangle \cr
& {\bf{u}} - 3{\bf{v}} = \left\langle {2,4, - 5} \right\rangle + \left\langle {18, - 30, - 6} \right\rangle \cr
& {\text{Add the vectors}} \cr
& {\bf{u}} - 3{\bf{v}} = \left\langle {2 + 18,4 - 30, - 5 - 6} \right\rangle \cr
& {\bf{u}} - 3{\bf{v}} = \left\langle {20, - 26, - 11} \right\rangle \cr} $$
