thank you for pointing out. It would've been much easier if the didn't insist 'Maybe' type.

The Ruby tests allow it, I did a really silly solution as I was in such a mood and I was surprised it passed. I even calculated the even and odds individually which makes no sense obviously.

A pure brute force algorithm won't be able to pass the tests. Try to study a math pattern in the triangle to speed up your code.

The ranking of 8kyu is for the whole kata. It is not possible to rank it harder for a single language.

I agree, this Kata seems far too difficult for an 8kyu problem.

Nope. Proof shown below using simultaneous equations.

Let {x = cows, y = chickens, L = legs, h = heads}

animals(heads=72, legs=200)

4x + 2y = L
x +  y  = H
-------------
4x + 2y = 200 (1)
2x + 2x = 144 (2)
-------------
     2x =  56
      x =  28      (cows)
      
Sub x = 28 into (1):

200 - (4 * 28) = 2y
      88       = 2y
      44       =  y   (chickens)

Your proposed answer:

Let {x = cows, y = chickens, L = legs, H = heads}

animals(heads=72, legs=200)

ASSUME chickens = 36, cows = 50

4x + 2y = 200 (1)
x +  y  = 72  (2)
--------------
50 + 36 = 86  (sub assumed x and y into (2))
86 != 72

∴ it is impossible

The initial code has been setup incorrectly, I fixed it by slightly modifying the initial code. Change "module animals where" to "module Animals where" and tell me if it works.