We see a right triangle here.
Use the Pythagorean Theorem:
a^2+b^2=c^2
a & b=legs
c=hypotenuse
a^2+15^2=20^2
a^2+225=400
a^2=175
a=13.2287565553
a=13.2
The missing side is 13.2cm
X/1000=72/125 multiply both sides by 1000
x=72000/125
x=576
So the fraction is 576/1000
So u have to add all the sides up.
which will give you 6 + 6√3 + 6 +6√3
because their opposite and parallel lengths and widths are equal
that gives you 12 + 12√3
so ans is 12m + 12√3m