A. The word mean is the same as saying average. To find the average/mean add all the numbers together and then divide by the amount of numbers. For example, if your numbers were 2, 6, and 7. You would do 2+6+7=15. Then 15 divided by 3 is 5. The mean of those numbers is 5.
B. The median is the middle number. Put the numbers in a list from least to greatest and then find the one in the middle. For example, if your numbers were 1, 2, 3, 4, 5, 6, the median would be 3.
C. The mode is the most frequent number. Count how many of each number appears in the list, the one with the most is the mode. For example, if your numbers were 1, 1, 3, 8, 2, 1, the number 1 would be the mode because it appears the most frequently.
D. The range is the smallest number and the largest number. If your numbers were 2, 12, 46, and 9, the range would be 2-46 or 2 to 46.
I hope this helps you, let me know if you have any questions or would like another example! :)