Question 517397
12 ounce bottles -------x
1 quart bottle-----------y

x-y=2100.............1
0.08x+0.11y=310.50

multiply by 100
8x+11y=31050.........2

1	x		-1	y	=	2100	.............1	
8	x	+	11	y	=	31050	.............2	
Eliminate y								
multiply (1)by 		11						
Multiply (2) by		1						
11	x		-11	y	=	23100		
8	x		11	y	=	31050		
Add the two equations								
19	x				=	54150		
/	19							
x	=	2850      			
plug value of 			x	in (1)				
1	x	+	-1	y	=	2100		
2850		+	-1	y	=	2100		
			-1	y	=	2100		-2850
			-1	y	=	-750		
				y	=	750