In a room containing 28 people, there are 18 people who speak English, 15 people who speak Hindi and 22 people who speak Kannada, 9 persons speak both English and Hindi, 11 persons speak both Hindi and Kannada where as 13 persons speak both Kannada and English. How many people speak all three languages?

The recurrence relation $$\,\,\,\,\,$$ $$T\left( 1 \right) = 2$$
$$T\left( n \right) = 3T\left( {{n \over 4}} \right) + n$$ has the solution $$T(n)$$ equal to

The number of substrings (of all length inclusive) that can be formed from a character string of length $$n$$ is

How many sub strings can be formed from a character string of length $$n$$?