To determine the moment of inertia of a uniform disc about the x-axis using the parallel axis theorem, one must first calculate the moment of inertia about the center of the disc. The parallel axis theorem states that the moment of inertia about any axis parallel to one through the center of mass can be found by adding the moment of inertia about the center of mass to the product of the mass and the square of the distance between the two axes. For a uniform disc, the moment of inertia about the center is (1/2)MR², and the distance from the center to the edge is R. Therefore, the moment of inertia about the x-axis is (1/2)MR² + MR², resulting in (3/2)MR².