Post what the question actually asks you for. It seems unlikely that you were asked to solve this, more likely you were asked to show it is true.
What it is doing is simplifying the denominator:
CB
consider also that when you divide fraction one with fraction two, then it's the same as fraction one multiplied by fraction two "upside down".
For instance . 2 writtin as a fraction is so we get
(remember that you have to write 'upside down' so in this case its ) and then we get