Answer:
18
Step-by-step explanation:
Okay first we know that for every one baboon there is 2 orang-utans (6 / 3 = 2)
So, I like to play the guess and check:
Lets just use the numbers 12 orang-utans and 6 baboons. We know that those two don't equal 27, so thats not it.
Now we can have 18 orang-utans and 9 baboons. 18 + 9 = 27, which means there are 18 orang-utans.
Hope this helps, and have a good day.