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tan(45°) is 1, so the vertical line above Z must be of length 9 for this to be true. This means WX also has length 9.  The line VZ is √(9²+9²) = 9√2 from Pythagoras.  The length of the perimeter is therefore given by:

$${\mathtt{9}}{\mathtt{\,\small\textbf+\,}}{\mathtt{6}}{\mathtt{\,\small\textbf+\,}}{\mathtt{9}}{\mathtt{\,\small\textbf+\,}}{\mathtt{6}}{\mathtt{\,\small\textbf+\,}}{\mathtt{9}}{\mathtt{\,\times\,}}{\sqrt{{\mathtt{2}}}} = {\mathtt{42.727\: \!922\: \!061\: \!357\: \!855\: \!4}}$$

or 42.73 to two decimal places.