Let's say o is the height of an ostrich and k is the height of a kiwi. 4k is four times the height of a kiwi. 4k + 20 is 20 inches more than 4 times the height of the kiwi, so o = 4k + 20.
I can't solve this without knowing the height of the ostrich, so if you have that comment and I'll edit the answer.