The question has a slight misprint. It should be what Bhagirathi says in the comments.
Nevertheless,
$\small \Bigl | A \cup B \cup C \Bigr | = |A| + |B| + |C| - \Bigl | A \cap B \Bigr | - \Bigl | A \cap C \Bigr | - \Bigl | B \cap C \Bigr | + \Bigl | A \cap B \cap C \Bigr |$
- $A \equiv $ Students who have taken Programming.
- $B \equiv $ Students who have taken Data Structures.
- $C \equiv $ Students who have taken Computer Organisation.
So, the number of students who have taken any of the $3$ courses is given by:
$| A \cup B \cup C| = |A| + |B| + |C| -| A \cap B | - | A \cap C| - | B \cap C | + | A \cap B \cap C|$
$ \qquad\qquad\quad \;= 125 + 85 + 65 - 50 - 35 - 30 + 15= 175$
Therefore, the number of students who haven't taken any of the $3$ courses is: $200 - 175 = 25$
Hence, the answer is Option C.