You don't say which charge is where. Are we to assume that the first named charge, \(\displaystyle 1.7\times 10^{-7}\) C, is at A and the second named charge, \(\displaystyle 5.3 \times 10^{-7}\) C is at B?

If so this is pretty much just straight computation. The electric field at distance r from charge Q is give by \(\displaystyle k_e\frac{Q}{r^2}\) where \(\displaystyle k_e= 9\times 10^{9}\) \(\displaystyle Nm^2/C^2\), "Coulomb's constant". Then add the field strength due to the two charges separately.