Possible Clues:

• Numerical calculations
• Rich mate's tight with it, being kind of mean
• One of the three R's
• The third letter after Q
• School subject, possibly thematic, includes religious instruction
• I abandon heart of subject in semi-coherent summing up maybe
• Putting two and two together, say
• One of the Rs
• Crime that somehow involves one in manipulation of figures
• Numerical maths