To find the difference between the boiling point of oxygen and the boiling point of hydrogen, you subtract the boiling point of hydrogen from the boiling point of oxygen:
\[ \text{Difference} = \text{Boiling point of oxygen} - \text{Boiling point of hydrogen} \]
\[ \text{Difference} = (-182.9 , \text{°C}) - (-252.87 , \text{°C}) \]
\[ \text{Difference} = -182.9 + 252.87 \]
\[ \text{Difference} = 69.97 , \text{°C} \]
So the difference between the boiling point of oxygen and hydrogen is 69.97.