The number of mainas and parrots in an aviary is in the ratio of (4x + 5) : 4x. If 25 mainas and 10 parrots are added to the aviary, then, the ratio would change to 5 : 3. How many mainas are there in the aviary at initial?
1
20
2
30
3
35
4
25
5
None of these