Question

How many times more hydroxide ions are there in a solution with a ph of 9 than in a solution with a ph of 3?

Answer 1

The pH unit has 10x as many hydrogens ions as the unit above.
Ex: A pH of 5 would have 10x more hydrogen ions than a pH of 6 
and 100x more than if it had a pH of 7.
With a pH of 9 and 3, this is equivalent to 10⁶
So your answer should be:
1,000,000