Hint : Let two oxide be M2Ox and M2Oy As per question
2a
16x
=
25
4
and
2a
16y
=
25
6
x=
a
50
,y=
3a
100
where a= atomic mass of Metal As x and y to be an integer, If we take a=50, then x=1,y=1.5 (not possible) If we take a=100 then x=2,y=3 (possible) ∴ Minimum Atomic Mass =100u