Explanation:
I just did in the other posting. how often did you post it ?
this is a trick question. the triangle at the top is not an isoceles triangle.
we use Pythagoras for an the steps.
so, the left part of the baseline (split by the height) is calculated by
12² = 10² + part²
144 = 100 + part²
part = sqrt(44) = 6.633249581... ft
the other part is then
20 - 6.633249581... = 13.36675042... ft
and the second leg of the large triangle is
leg² = 10² + 13.36675042...² = 278.6700168...
leg = 16.69341238... ft
P = 12 + 16.69341238... + 8 + 8 + 20 = 64.69341238... ft ≈
≈ 64.69 ft
please see the answer to the other posting for more details.