Unknown Charge and Electric Field in a Right Triangle

[kerbyjonsonjr]

Homework Statement

A right triangle is shown below. The charge on the right is unknown, but the electric field shown is only in the –x direction.
a. What is the unknown charge?
b. What is the magnitude of the electric field?

Homework Equations

The Attempt at a Solution

I have no idea how to start this problem. I have just been staring at it for 20 minutes. I would really appreciate any help.

 

[lachy89]

You have not posted any relevant equations. I think a good starting point would be looking for an equation for the electric field due to a point charge.

As you have explained the electric field is in the -x direction. Would this mean that there is no y component at the point in question?