In the reaction 2H2O2 - and get 2H2O plus O2 if you start with 4 H2O2 how much O2 will you end up with?

2H2O2 ===> 2H2O + O2

Note the molar ratiOS are 2 :: 2:1

So By the same ratiOS

4 :: 4:2 ==> 2 :: 2:1

4H2O2 ===> 4H2O + 2O2

Similarly

3H2O2 ===> 3H2O + 1.5O2

or

6H2O2 ===> 6H2O + 3O2

et seq.,