Absolute value "changes" at 0. Here you have two absolute values that involve "x" and "x- 3" so you should break this into three intervals: x< 0, \(\displaystyle 0\le x< 3\), and \(\displaystyle 3\le x\).
If x< 0 then x is also less than 3 so both |x- 3|= -(x- 3) is positive and so x|x- 3|= -x(x- 3) is negative. |x|x-3||= -(-x(x- 3)= x(x- 3).
If \(\displaystyle 0\le x< 3\) then x is positive but x-3 is negative so x|x- 3|= -x(x- 3) is positive. |x|x- 3||= -x(x- 3).
If \(\displaystyle 3\le x\) then x is also positive so x|x- 3|= x(x- 3) is positive. |x|x- 3||= x(x- 3).