The combined average weight of an okapi and a llama is 450450450 kilograms. The average weight of 333 llamas is 190190190 kilograms more than the average weight of one okapi. On average, how much does an okapi weigh, and how much does a llama weigh?

First of all, lets consider that you made a litte mistake and you meant this problem.........

"The combined average weight of an okapi and a llama is 450 kilograms. The average weight of 3 llamas is 190 kilograms more than the average weight of one okapi. On average, how much does an okapi weigh, and how much does a llama weigh?"

This is a system of two equations.

Let it be X the average weight of a LLAMA
And Y the average weight of an OKAPI

X + Y = 450 kg   1)
3X = 190 kg +Y   2)

So, with 1) we have that  Y = 450 - X
We subsitute in 2) and we have 

3X = 190 + (450 -X).............We solve for X ....==> 4X = 640kg ==> X = 160kg

..We replace X in 1 and get => Y = 450kg -X = 450kg -160kg = 290kg


160kg....... average weight of a LLAMA
290kg........average weight of an OKAPI