Equilibrium point with charges of opposite sign

Two point charges $q_1=-2.0\mu \mathrm{C}$ and $q_2=+8.0\mu \mathrm{C}$ are fixed in vacuum at $x=0$ and at $x=0.30\mathrm{m}$. Determine the point of the $x$-axis at which a third charge is in equilibrium.