Question 585573
part I   	5.50%	per annum---x					
part II	4.00%	per annum---y					
									
x+y=18000	------------------------1				
5.50%x	+4.00%y=831				
Multiply by	100							
5.5x+4y=83100.00--------2	
									
Multiply (1) by	-5.5						
we get									
									
-5.5	x	-5.5	y=			-99000.00			
									
Add this to (2)									
									
-1.5	y=-15900			
									
divide by		-1.5							
									
y=10600	
$10,600	investment at	4.00%
Balance $	7400	investment at	5.50%
CHECK									
10600	---------	4.00%	-------	424.00					
7400	-------	5.50%	-------	407.00					
Total			--------------	831.00