Question 562122
1/2 cup ---x numbers
full cup---y numbers

x+y =12

0.5x+0.75y=8
multiply by 100
50x+75y=800

these are the two equations solve for x & y 

1	x	+	1	y	=	12	.............1	
50	x	+	75	y	=	800	.............2	
Eliminate y								
multiply (1)by 		-75						
Multiply (2) by		1						
-75	x		-75	y	=	-900		
50	x		75	y	=	800		
Add the two equations								
-25	x				=	-100		
/	-25							
x	=	4   1/2 cup  			
plug value of 			x	in (1)				
1	x	+	1	y	=	12		
4		+	1	y	=	12		
			1	y	=	12		-4
			1	y	=	8		
				y	=	8 full cup