Answer
$$[x]_B=\left[ 3 \quad -5 \quad 11\right]^T.$$
Work Step by Step
Let $x=(3,-5,11)$ and $B=\{ (1,0,0),(0,1,0),(0,0,1) \}$
To find the coordinates of $x$ relative to $B$, we have to find the following;
$$\langle (3,-5,11),(1,0,0)\rangle = 3$$
$$\langle (3,-5,11),(0,1,0)\rangle = -5$$
$$\langle (3,-5,11),(0,0,1)\rangle = 11.$$
Then, the coordinate matrix of $x$ relative to $B$ is given by
$$[x]_B=\left[ 3 \quad -5 \quad 11\right]^T.$$
