In a Vizag survey, 65% watch the news and 40% watch serials, while 15% watch neither. The 1200 marked in the diagram watch both. How many watch only the news?

At least one $=85\%$, so both $=65+40-85=20\%$. 20% is 1200 people, so 1% is 60 and the survey has 6000 people. Only news $=65\%-20\%=45\%=2700$. 3900 is the whole 65%, 1200 is the both-group, and 2400 is the 40% who watch serials.