In a Business School, there are 20 teachers who teaches Business Math or Business Law. Of these, 12 teaches Business Math and 4 teaches both Business Math and Business Law. How many teach Business Law?

    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.