What number must be added to 15,-6,& 12 to have a mean of 5?

To get the mean, you add all of the numbers, and then divide the answer by the number of numbers.

15+(-6)= 9
9+12= 21
(21+x= q )⬅️ignore this for now, that's where the unknown number would have been

The mean = 5, and the number of numbers is 4, so basically, you find 5•4=20

So take the 21 from before, and if you add -1, you get 20!

So, x= ➖1⃣ (That's a -1)

Mean = sum of all numbers / no of numbers
so u have mean and three of ur numbers given
then
5=(15-6+12+x)/4 x is the number u need to find
then
20= 15-6+12+x multiplying both sides by 4
20=21+x addition and subtraction
20-21=x
x= -1

Hope i can you!