Question 901260
let x be the number of liters of water												
---	percent	----------------	Amount									
Alcohol	90	----------------			20	liters						
water	0	----------------			x	liters						
Mixture	50	----------------	20	+	x	liters						
												
90	*	20	+	0	x	=	50	(	20	+	x	)
1800	+	0	x	=	1000	+	50	x				
0	x		-50	x	=	-1800	+	1000				
-50	x	=	-800									
/	-50											
x	=	16		liters	water