A student's marks were incorrectly entered as 35 instead of 99. Due to this, the average marks of the class got decreased by 83. What is the number of students in the class?

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).