Answer:
n = 19.
Explanation:
If there are x guinea pigs then there are 3/2 x and 2/3 x rats.
So n = x + 3/2 x + 2/3 x
n = 19x / 6
19x = 6n
Let x = 6 , then n = 19*6 / 6 = 19.
Now n and x must be whole numbers so x is 6 and n = 19 are the smallest possible values.