Answer:

vector with direction equal to the axis X.
Step-by-step explanation:
We use the Gauss Law and the superposition law in order to solve this problem.
Superposition Law: the Total Electric field is the sum of the electric field of the first infinite sheet and the Electric field of the second infinite sheet:

Thanks Gauss Law we know that the electric field of a infinite sheet with density of charge σ is:

Then:

This electric field has a direction in the axis perpendicular to the sheets, that means it has the same direction as the axis X.