Finding the Charge on an Ion in a Zero Electric Field

[Noreturn]

Homework Statement

A proton is at the origin and an ion is at x1 = 6 nm
If the electric field is zero at x2 = -3 nm , what is the charge on the ion?

Homework Equations

for ion

The Attempt at a Solution

https://imgur.com/ryyuQBq

I just have used all my attempts besides one. So I believe I keep getting the right answer just not in terms of e. Cause I keep getting 3.6x10^-19 which when you divide by 1.602 I get the same answer of -2e.

Can anyone confirm this?

Now that I redid the math Looks like I made a input error the actual answer is -9e ?

 

[Orodruin]

-9e is correct. The proton is three times closer and $3^2=9$.