It's going to be hard to provide hints to the answer this week.
Edit: My hint was "Be" which is the symbol for Berylium, element 4 on the periodic table.
A: 4 students (3 with blue eyes and 1 without).
The probability the first child has blue eyes is 3/4. Once that child is taken out of consideration, there are 2 children with blue eyes out of 3 so the probability is 2/3. Multiplying that together, we have 3/4 x 2/3 = 2/4 = 1/2
An alternate way to think of it is that there are 6 pairings of the 3 children. In 3 of those pairings you'll have two blue-eyed children. In the other 3 pairings it will be the brown-eyed child with one of the blue-eyed children. So exactly half of the pairing are two blue-eyed children and the other half are a brown and a blue-eyed child.