Please explain me its answer in detail in terms of avg. Oxidation state

Since Fe and O are in the ratio 0.93:1.Thus we can proportionate the ratio as 93 : 100
Let the atoms of Fe in +3 O.S. be = x
Let the atoms of Fe in +2 O.S. be = 93-x
Let the atoms of O in -2 O.S. be = 100

Since the total charge is zero thus we can write,
3*x + 2*(93-x) -2*100 = 0
3x + 186 – 2x – 200 =0
x = 14
% of Fe in +3 state = (14/93)*100
= 15%

Approved