lets suppose,
R is right eye sighted only (left eye blind)
L is left eye sighted only (right eye blind)
B is both eyes sighted
N is no eyes sighted (blind)
We can deduce the following equations based on what we've been given:
1) R+B=2
2) L+B=3
3) N+R=4
4) N+L=5
subtract equation 1 from equation 2
L-R=1
The smallest number we can start with is 1.
Let's assume that R=1, and determine the other values based on this assumption.
1) B=1
2) N=3
3) R=1
4) L=2
So we can calculate that Linus saw 7 total bats that night. and they might have been 4 blind, 2 full sighted and 1 blind in the right eye only