What add to - 17 and multiplies to 86

In this question the thing that you want to know is a number that adds with - 17 and becomes equal to the multiplication of 86 with the unknown number. Based on this assumption i will proceed with the following problem. Now getting back to the problem given.

Let us assume the unknown number = x

Then we can create an equation for solving the problem.

-17 + x = x * 86

-17 + x = 86x

-17 = 86x - x

-17 = 85x

x = - 17/85

= - 5

So the unknown number is - 5. This is the method to solve the required equation.