Two friends were asking each others some questions.
One of them asked the following question to the other.
If 2 giraffes have 4 eyes in total,
2 cats have 4 eyes in total, and
a pigeon has 2 eyes, then how many eyes do we have?
In the question it is asked "How many eyes do 'we' have".
So it refers to 2 people (the 2 friends).
So there will be a total of 4 eyes.