The average of 6 numbers is 7. When a 7th number is addedThe average of all numbers is 0. What is the seventh number?

- - The average of 6 numbers is 7.

So those 6 numbers must add up to 42.

- - If one more number results in an average of zero,

the new number must be - 42.

Then all 7 numbers add up to zero.