Answer:
6
Explanation:
First, find the total number for the set of four numbers. To do this, multiply 3.5 and 4. We do this because the mean is division, so we need to get back to the original amount.
3.5 x 4 = 14
Next, we need to find the other total when the mean is 4. There are 5 numbers, which tells us we had to divide the total by 5 to get 4. So, again, we want to multiply the mean, 4, and the 5 to get the total.
5 x 4 = 20
Finally, find the number we added in. To do this, we subtract the two totals.
20 - 14 = 6