Question

The electric field E = (5.4, 2.7, 8.1) N/C passes through a square surface whose area vector is A = (1.7, −3.4, 0.55) m2. What is the electric flux ΦE through the surface?

Answer 1

If the square surface has no charge then the electric flux will also be 0 \[\phi =\]

Answer 2

I think Mustaafa isn't quite right, what he stands is true (and it is Gauss' Law) only for closed surfaces, i.e., the Flux \[\Phi _{E}=\frac{q}{\epsilon_{0}}\], where \[\ q \] is the total charge enclosed by the CLOSED surface.
In this case we have an open surface, so you should calculate the flux through it using:
\[\ \Phi_{E} = E * A \], where * stands for the Dot product. Good Luck ;)