Average selling price of article II by shop A and B is 3608 , so total selling price of both will be 7216 

Writing in equation form :
Let “x “ be the market price which is same for all shops , discount rate of A for article II is 14 % , let “y “ be the discount rate for shop B
7216 = (100 - 14 /100) * X + (100 - Y /100) * X
7216 = x/100 * (86 + 100 - y)
7216 = x/100 * (186 - y).......(i)
Also ,
Average selling price of article II by shop B and C is 3300 , so total selling price of both will be 6600
Writing in equation form :
Let “x “ be the market price which is same for all shops , discount rate of C for article II is 28 % , let “y “ be the discount rate for shop B.
6600 = (100 - y /100) * X + (100 - 28 /100) * X
6600 = (100 - y /100) * X + 72x /100
6600 = x /100 * (172 - y).......(ii)
subtracting both equations, we get
616 = 14 * x/100
So market price = 4400
Discount offer by B can be found by substituting x in any one of the equation
Y = 22%
Disount amount = 4400 * 22 / 100
Discount amount = 968