Problem $2$: $(25\%$ of Assignment Value$)$

Two charges $-q_1=1\mathrm{.}3{10}^{-6}C,q_2=3\mathrm{.}6{10}^{-6}C-$ are separated by a distance of $d=1\mathrm{.}5m.$

At what distance, $r$ in meters, from the first charge is the electric field zero?