There is no need to calculate the Force in this equation. There is enough information to just calculate the electric field.
The formula for electric field is as follows:
where ke = 8.988 * 10^9
q = charge
r = distance
However, since there is more than one charge, you would need to take the sum to get the total electric field.
This formula will reflect that:
Plug in the values into the formula, and take the sum and that should get you the correct answer.
Note that the distance, r, will be different for q1, you can find this r by using pythagorean theorem.
Please comment if you need more help.