Solution:
If valency factor is 2, then equivalent weight will be equal to half its molecular weight.
In the oxidation state of Mn is +II
In , the oxidation state of Mn is +III
In , the oxidation state of Mn is +IV
In , the oxidation state of Mn is +VII
In , the oxidation state of Mn is +VI
Thus, when is converted into , then the valency factor is 2, and the equivalent weight of will be half of its molecular weight.