Mean = (10 + 12 + 14 + 16) / 4 = 13. Variance = [(10-13)² + (12-13)² + (14-13)² + (16-13)²] / 4 = 2.5.

Mean = 5. Variance = [(2-5)² + (4-5)² + (4-5)² + (4-5)² + (5-5)² + (5-5)² + (7-5)² + (9-5)²] / 8 = 5.

The total age of the original group is 20 * 15 = 300. Adding the new student gives 300 + 22 = 322. The new average age is 322 / 16 = 20.125, which rounds to 20.6.

Let the number of students be n. Total height = 150n. After one leaves, total height = 148(n - 1). Setting the equations gives 150n - 148(n - 1) = height of student.

Total height = 160 * 10 = 1600 cm. New total = 1600 - 170 = 1430 cm. New average = 1430 / 9 = 158.89 cm, approximately 159 cm.

Total score = 75 * 10 = 750. New total = 750 - 90 = 660. New average = 660 / 9 = 73.33.

The mode is 2, as it appears four times in the data set.

The mode is 3, as it appears 3 times, which is more than any other number.

The mode is 50, which appears 3 times in the scores.

Total marbles = 5 + 3 + 2 = 10. Green or yellow = 5 + 3 = 8. Probability = (Green + Yellow) / Total = 8/10 = 4/5.

Total marbles = 5 + 7 + 8 = 20. Green or yellow = 5 + 7 = 12. Probability = 12/20 = 3/5.

Total marbles = 5 + 3 + 2 = 10. Probability of red or yellow = (Number of red + Number of yellow) / Total = (5 + 2) / 10 = 7/10.

Total marbles = 5 + 3 + 2 = 10. Probability of drawing a yellow marble = Number of yellow marbles / Total marbles = 2/10 = 1/5.

Total marbles = 5 + 3 + 2 = 10. Probability of picking a yellow marble = Number of yellow marbles / Total marbles = 2/10 = 1/5.

Let the number of items be n. Then, 15n - x = 12(n - 1). Solving gives x = 18.

Let the number of elements be n. Then, 20n - x = 18(n - 1). Solving gives x = 22.

Standard deviation is the square root of variance. Therefore, SD = √36 = 6.

The number 40 appears most frequently (4 times), so the mode is 40.

The number 4 appears 3 times, which is more than any other number, making it the mode.

Let the fourth score be x. Mean = (70 + 80 + 90 + x) / 4 = 85. Thus, 240 + x = 340, so x = 100.

Mean = (80 + 85 + 90 + 95 + x) / 5 = 90. Solving gives x = 100.

Average = (70 + 80 + 90) / 3 = 240 / 3 = 80.

Mean = (80 + 85 + 90 + 95 + x) / 5 = 90.\n\n350 + x = 450\n\nx = 450 - 350 = 100.

Average = (80 + 85 + 90 + 95) / 4 = 350 / 4 = 87.5, which rounds to 88.

Let the fourth score be x. (80 + 85 + 90 + x) / 4 = 85. Therefore, 255 + x = 340, so x = 85.

Mean = (80 + 85 + 90 + x) / 4 = 85.\n\n255 + x = 340\n\nx = 340 - 255 = 85.

The current total score is 80 + 90 + 70 = 240. To achieve an average of 85 over 4 subjects, the total score must be 4 * 85 = 340. Therefore, the score needed in the fourth subject is 340 - 240 = 100.

Banana has the highest count (8), so the mode is Banana.

The mode is Apple, as it appears three times in the survey results.

The mode is 3, as it appears three times, more than any other number.