Answer
$$[x]_S=\left[ \begin {array}{ccc} 7\\ -4\\ -1\\ 2\end {array} \right].$$
Work Step by Step
Since we have
$$x= 7(1,0,0,0)-4(0,1,0,0)-(0,0,1,0)+2(0,0,0,1),$$
then the coordinate matrix of $x$ in $R^3$ relative to the
standard basis is
$$[x]_S=\left[ \begin {array}{ccc} 7\\ -4\\ -1\\ 2\end {array} \right].$$