You can know the n-factor.

1st case:- n-factor=5 [Mn(7) to Mn(2)]

Now, this is one of the best concepts of mole concept,

"The EQUIVALENTS(normality×volume) of all reactants and products are EQUAL."

N=M×n-factor

Thereby, (100ml)(0.05N)=(100ml)V

Do the same in the next case but n-factor in 2nd case is 3.

Solve it further by yourself, it will help you to gain confidence.