Let the nuber of adviseers who advise Concern Math and Concern Jurisprudence are denoted by BM and BL respectively.
Such as we keep,
BM or BL = 20
BM = 12
BM and BL = 4
Therefore using the jurisprudence of formal hypothesis we keep,
(BM or BL) = BM + BL – ( BM and BL)
20 = 12 + BL – 4
BL = 20 -12 + 4 = 12
Hence the reckon of adviseers who advise concern jurisprudence is 12.