It appears that x_t to fbx conversion represents attempts to transform 3D models from Parasolid format (.x_t) to Autodesk Kaydara 3D format (.fbx). This is likely possible, but perhaps more typically done with a middle step through conversion to some generic, widely accepted exchange standard.
Convert Parasolid model (text) to Autodesk Kaydara 3D data exchange format.
We found one software available in the database for this conversion.
Microsoft Windows software - convert x_t to fbx on Windows
A 3D CAD translation softwate
Convert from x_t file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.