For the three rational number a, b and c; which of the following is correct:

1. a ÷ b = b ÷ a
2. a x (b ÷ c) = (a ÷ b) x (a ÷ c)
3. a ÷ (b ÷ c) = (a ÷ b) ÷ (a ÷ c)
4. a ÷ (b ÷ c) ≠ a ÷ b ÷ c