In a Business School there are 20 teachers who teaches Busin

Solution

Let the nuber of teachers who teach Business Math and Business Law are denoted by B_M and    B_L respectively.

Such as we have,

B_M or B_L = 20

B_M = 12

B_M and B_L = 4

Therefore using the law of set theory we have,

(B_M or B_L) = B_M + B_L - ( B_M and B_L)

20 = 12 + B_L - 4

B_L = 20 -12 + 4 = 12

Hence the number of teachers who teach business law is 12.