Answer:
8
Step-by-step explanation:
If the mode is 3, there are at least 2 elements that are 3. If the largest is 9, there is one element that is 9. If the smallest is -3, there is one element that is -3. That accounts for 4 of the 5 elements of the set. The last element, X, must have a value such that the average is 4.
(-3 +3 +3 +9 +X)/5 = 4
12 +X = 20 . . . . . multiply by 5, simplify
X = 8 . . . . . . . . subtract 12
The second-largest element in A is 8.
