Question 426992
$5 bills		x 							
$20 bill	------------	y							
x+y=	54	.............1			
5x+20y	=780	.............2			
										
multiply (1)by	-20								
Multiply (2) by	1								
-20x-20y	=-1080				
5x+20y=780				
Add the two equations	

-15x=-300				
/-15									
x=20 $5 bills				
plug value of 	x in (1)						
										
x+y=54				
20+y=54				
y=54-20
y=34			
y=34 $20 bill