Question 3805
the unknown number: x
the unknown number increased by 8: x + 8
a product of the unknown number multiplied by -4: - 4x


If x + 8 is the difference between x and - 4x, then x + (x + 8) is equal to - 4x, so... 


x + (x + 8) = - 4x | re-arranging
2x + 8 = - 4x | - 2x on both sides
8 = -6x | : -6 on both sides
- 1 1/3 = x