Let us set up a proportion.
4/3 = 18/t
Let t = height of giraffe (in inches)
We also have to change units to make our math work easier.
There are 12 inches in one foot.
So, 3 feet = 36 inches and 18 feet = 216 inches.
Our new proportion set up is:
4/t = 36/216
36t = 4(216)
36t = 864
t = 864/36
t = 24
The toy giraffe is 24 inches tall.