Question 450357
------	percent	----------------	quantity										
dilute acid	20----------------5	gallons							
pure acid	100----------------x	gallons							
Total	50	----------------5+x	gallons							
													
20*5+100*x=50(5+x)								
100+100	x=250+50x					
100x-50x=250-100					
50x=150										
/50										
x=3 gallons	100	%	pure acid