Question 552053
Total = $42,000 
5%, 
7%,
 and 9%
 interest $2,600. 

7% ----------x
9%-----------y
5%----------(x+y-200)

Total investment 
x+y+x+y-200 = 42000
2x+2y=42000+200
2x+2y=42200
/2
x+y=21100................(1)
Interest
perecntages have been converted by multiplying the equation by 100
7x+9y+5(x+y-200)= 2600*100
7x+9y+5x+5y-1000=260000
12x+13y=260000+1000
12x+13y=261000..............(2)


1	x	+	1	y	=	21100	.............1	
12	x	+	13	y	=	261000	.............2	
Eliminate y								
multiply (1)by 		-13						
Multiply (2) by		1						
-13	x		-13	y	=	-274300		
12	x		13	y	=	261000		
Add the two equations								
-1	x				=	-13300		
/	-1							
x	=	13300    			
plug value of 			x	in (1)				
1	x	+	1	y	=	21100		
13300		+	1	y	=	21100		
			1	y	=	21100		-13300
			1	y	=	7800		
				y	=	7800
x+y-200 = 13300+7800-200=21900

$13,300@ 7%
$7800 @ 9%
20,900 @ 5%

m.ananth@hotmail.ca