Question 473930
Solution:-

Regular	1	
Deluxe	2		
Total   3	

Now
Using nCr=n! /(n-r)! r!

3 things can be chosen out of 11 	= 11C3 ways.
					= 11!/(11-3)!3!
					= 11!/ 8!3!
					=(11*10*9*8!) / (8! * 3*2*1)
					= (11*10*9) /(3*2*1)
					= 990 /6
					= 165 ways
1 Regular can be chosen out of 4 	= 4C1 
  	= 4! /(4-1)!1!
  	=4*3!/3!1!
   	= 4 ways 
2 Delux can be chosen out of 7 		= 7C2
					=7!/(7-2)!2!
					=7!/5!2!
					=7*6*5!/5!2!
					=7*6/2
					=42/2
					=21 ways

P(exactly 2 are deluxe model)		=  (7C2 * 4C1) / 11C3
					= (21*4) /165		
					=84/165
					=0.509