Answer
See attached file for drawing.
Work Step by Step
The right angles are consecutive. By dividing the figure into a rectangle and triangle, you will be able to find the missing side length by using the 30-60-90 rule.
Example.
You can determine the base of the triangle you formed by subtracting 12 from 18. This gives you 6m.
From the Pythagorean Theorem you can determine the length of the missing side.
$a^{2}$+$b^{2}$=$c^{2}$
$8^{2}$+$6^{2}$=$c^{2}$
64+36=$c^{2}$
100=$c^{2}$
10=c (This is the missing side length.)
You now could find the perimeter by adding all sides.
8+12+18+10=48m
