To find the average of different numbers, first you add them all up. So -5+-7+-2+2+-3+=-15. Then, you divide the sum of all the numbers by the amount of numbers there were. So in this case, there were 5 numbers so we would divide the sum of all of them by 5. So now we do -15/5=-3.
Another example of finding the average of numbers is 15+4+10+9+3+1. So first we add them up and we get 42, then again, we divide by the amount of numbers there are. So we do 40/6 and we get 7, so the average is 7.
If there are n coins, then the smallest (minimum) amount of coins we need to flip is 1. The reason why is because the best case scenario would be flipping all heads except the last coin which is tails. This scenario is rare if n is large, but still possible.
