If cos3A = X, then value of X?

$$ {4\over 5}×[{1\over 2}\ of\ 25]+12÷{3\over 4}-32=?$$

If the circumradius of an equilateral triangle ABC be 8 cm, then the height of the triangle is 

What is the measure of the circum radius of a triangle whose sides are 9cm, 40cm and 41cm?

Study the following information carefully to answer the questions.
The teachers' colony has 2800 members, out of which 650 members read only English newspaper. 550 members read only Hindi newspaper and 450 members read only Marathi newspaper. The number of members reading all the 3 newspapers is 100. Members reading Hindi as well as English newspapers are 200. 400 members read Hindi as well as Marathi newspaper and 300 members read English as well as Marathi newspaper.

Find the number of members reading Hindi newspaper.

A box contains 10 red ball, 6 green ball if 2 balls are drawn randomly what is the probability of getting non-green ball?

The difference between CI and SI on a sum of money for 3 years at 5% per annum is Rs.61. Find the sum.