Figure 1 depicts two long, thin, parallel lines of charge, separated by a distance $l$. Line one is located at the origin of the $x$ axis and holds a charge per unit length of $\lambda_1$ C/m. Line two is located at the coordinate $x = l$ and holds a charge per unit length of $\lambda_2$ C/m.
Both $\lambda_1$ and $\lambda_2$ have the same sign of charge, and the relative magnitudes of the charge densities are:
$$\lambda_1 = 3\lambda_2$$
At what value of $x$ between line one and line two is the net electric field equal to zero? Answer in units of the distance $l$.