Question 563567
let them sell x pieces at $9.50
and y pieces at $7.50

x+y=90
9.5x+7.5y=713

$9.50			x	numbers				
$7.50			y	numbers				
								
1	x	+	1	y	=	90	.............1	
9.5	x	+	7.5	y	=	713	.............2	
Eliminate y								
multiply (1)by 		-7.5						
Multiply (2) by		1						
-7.5	x		-7.5	y	=	-675		
9.5	x		7.5	y	=	713		
Add the two equations								
2	x				=	38		
/	2							
x	=	19  			
plug value of 			x	in (1)				
1	x	+	1	y	=	90		
19		+	1	y	=	90		
			1	y	=	90		-19
			1	y	=	71		
				y	=	71
$9.50			19    	numbers				
$7.50			71    	numbers				
m.ananth@hotmail.ca