Question

A teacher wrote the numbers 10 ,-2, 4, 3, -1, -7 ,1 on a white board.the teacher asked which number should she write in order to make the sum of all the numbers equal to zero?

Answer 1

Let x be that number:

x +10 -2 +4 + 3 - 1 - 7 +1 = 0

 x +8 = 0

and x = - 8