Question 572498
Solution A
Amount = x 
Concentration =30% =0.3


Solution B
Amount = 20 
Concentration =70% = 0.7


Resultant Solution
Amount =20+x 
Concentration =40%=0.4

[Amount Solution A * Concentration A] + [Amount Solution B * Concentration of B] = Amount of Resultant * Concentration of resultant

(x)(0.3)+(20)(0.7)= (20+x)(0.4)
0.3x+14=8+0.4x
0.3x-0.4x=8-14
-0.1x=-6
-0.1x/-0.1=-6/-0.1
x=60



Solution A
Amount = x = 60 liters
Concentration =30% =0.3




60 liters of a 30% alcohol solution must be mixed with 20 liters of a 70% solution to get a 40% solution?