The average runs scored by a batsman in 21 matches is 41. In the next 15 matches, the batsman scored an average of 13 runs. Find his average runs (rounded off to two decimals) in all the 36 matches.

The average of 100 numbers is 40. If one of the numbers, 30, is replaced by 70 while keeping the other numbers same, what is the new average?

The arithmetic mean of 22.5, 56, 42.5, 2x + 1, x - 2, 3x, and 36 is 30. Find the value of x (where x > 0).