In the given diagram, we are working with areas of squares inscribed in a circle. The points and lines are defined such that:
- The area of the square \( PXWR \) is the area enclosed by the tangent line \( PX \) and the radial line from the center \( R \).
- Similarly, the areas of the other squares \( RUVZ \) and \( SPQT \) are determined by the distances defined by the lines and the tangents.
By analyzing the geometric relationships and using the fact that the squares are inscribed, the correct relation between the areas of these squares is:
\[
\text{Area of SPQT} = \text{Area of PXWR} - \text{Area of RUVZ}.
\]
This is derived from the fact that the areas of the squares depend on the lengths of the sides, and the side lengths are related in such a way that this equation holds. Therefore, the correct answer is (B).