Define the given quantities and set up the coordinate system.

Let $q_1 = 0.700 \text{ nc} = 0.700 \times 10^{-9} \text{ C}$ and $q_2 = 9.00 \text{ nc} = 9.00 \times 10^{-9} \text{ C}$.
The distance between the charges is $d = 1.40 \text{ m}$.
Let $q_1$ be at the origin ($x=0$) and $q_2$ be at $x=d$.
Let the point where the electric field is zero be at a distance $x$ from $q_1$.
The distance from $q_2$ to this point will then be $d-x$.

The magnitude of the electric field due to a point charge $q$ at a distance $r$ is given by $E = k \frac{|q|}{r^2}$, where $k$ is Coulomb's constant.
For the total electric field to be zero at point $x$, the electric field due to $q_1$ ($E_1$) must be equal in magnitude to the electric field due to $q_2$ ($E_2$).

We can cancel $k$ from both sides:

Cancel $10^{-9}$ from both sides:

Take the square root of both sides:

Cross-multiply:

Rounding to three significant figures, the point where the total electric field is zero is: