Assign oxidation number for each of the following

Question

a: KMnO4
b: (NH4)2HPO4
c: P4O6

Answer 1

a:
K has an oxidation number of +1
Mn has an oxidation number of +7
O has an oxidation number of -2

b:
N has an oxidation number of -3
H has an oxidation number of +1
P has an oxidation number of +5
O has an oxidation number of -2

c:
P has an oxidation number of +3
O has an oxidation number of -2