$\square+\square+\square=30$, with boxes filled using $1, 3, 5, 7, 9, 11, 13, 15$, possibly repeated. How? From the days I started to learn Maths, I've have been taught that 


  Adding Odd times Odd numbers the Answer always would be Odd; e.g., 
  $$3 + 5 + 1 = 9$$


OK, but look at this question 



This question was solved and the answer was 30, how it was possible? Need a valid explanation please.
You have answered your own question: the sum of an odd number of odd numbers must be odd. Therefore it cannot equal 30.

You should not believe everything you read in a photo on the internet.
It's
$$3_3+3_3+3_3=30.$$
Where $3_3$ is read as 3 base 3.